diff --git a/src/bids/index.js b/src/bids/index.js
index 992df04b..c6548af1 100644
--- a/src/bids/index.js
+++ b/src/bids/index.js
@@ -1,7 +1,7 @@
 import { buildBidsSchemas } from './schema'
 import { BidsJsonFile, BidsSidecar } from './types/json'
 import { BidsTsvFile } from './types/tsv'
-import { BidsHedIssue, BidsIssue } from './types/issues'
+import { BidsHedIssue } from './types/issues'
 import BidsHedSidecarValidator from './validator/sidecarValidator'
 import BidsHedTsvValidator from './validator/tsvValidator'
 
@@ -9,7 +9,6 @@ export {
   BidsTsvFile,
   BidsJsonFile,
   BidsSidecar,
-  BidsIssue,
   BidsHedIssue,
   BidsHedSidecarValidator,
   BidsHedTsvValidator,
@@ -20,7 +19,6 @@ export default {
   BidsTsvFile,
   BidsJsonFile,
   BidsSidecar,
-  BidsIssue,
   BidsHedIssue,
   BidsHedSidecarValidator,
   BidsHedTsvValidator,
diff --git a/src/bids/tsvParser.js b/src/bids/tsvParser.js
index 46557b6e..9e9e5c6a 100644
--- a/src/bids/tsvParser.js
+++ b/src/bids/tsvParser.js
@@ -13,7 +13,7 @@ const isContentfulRow = (row) => row && !/^\s*$/.test(row)
  * Parse a TSV file.
  *
  * @param {string} contents The contents of a TSV file.
- * @returns {Map} The parsed contents of the TSV file.
+ * @returns {Map<string, string[]>} The parsed contents of the TSV file.
  */
 export function parseTSV(contents) {
   const columns = new Map()
@@ -40,7 +40,7 @@ export function parseTSV(contents) {
  * Convert parsed TSV file data from the old BIDS format to the new BIDS format.
  *
  * @param {{headers: string[], rows: string[][]}} oldParsedTsv Parsed TSV data using the old format
- * @returns {Map} The parsed contents of the TSV file, using the new format.
+ * @returns {Map<string, string[]>} The parsed contents of the TSV file, using the new format.
  */
 export function convertParsedTSVData(oldParsedTsv) {
   const columns = new Map()
diff --git a/src/bids/types/file.js b/src/bids/types/file.js
index 78788e11..af46fe07 100644
--- a/src/bids/types/file.js
+++ b/src/bids/types/file.js
@@ -13,7 +13,7 @@ export class BidsFile {
 
   /**
    * The Object representing this file data.
-   * This is used to generate {@link BidsIssue} objects.
+   * This is used to generate {@link BidsHedIssue} objects.
    * @type {Object}
    */
 
@@ -40,7 +40,7 @@ export class BidsFile {
    * Validate this validator's tsv file.
    *
    * @param {Schemas} schemas - The HED schemas used to validate this file.
-   * @returns {BidsIssue[]} - Any issues found during validation of this TSV file.
+   * @returns {BidsHedIssue[]} - Any issues found during validation of this TSV file.
    */
   validate(schemas) {
     if (!this.hasHedData) {
@@ -63,9 +63,19 @@ export class BidsFile {
     }
   }
 
+  /**
+   * Determine whether this file has any HED data.
+   *
+   * @returns {boolean}
+   */
+  get hasHedData() {
+    return false
+  }
+
   /**
    * The validator class used to validate this file.
-   * @returns {BidsValidator}
+   *
+   * @returns {function} (typeof BidsValidator) A subclass constructor of {@link BidsValidator}.
    */
   get validatorClass() {
     return this._validatorClass
diff --git a/src/bids/types/issues.js b/src/bids/types/issues.js
index 36173918..a398b511 100644
--- a/src/bids/types/issues.js
+++ b/src/bids/types/issues.js
@@ -1,13 +1,13 @@
 import { generateIssue, IssueError } from '../../issues/issues'
 
-const bidsHedErrorCodes = new Set([104, 106, 107])
+const bidsHedErrorCodes = new Set(['HED_ERROR', 'HED_INTERNAL_ERROR'])
 
-export class BidsIssue {
+export class BidsHedIssue {
   /**
    * The BIDS issue code.
-   * @type {number}
+   * @type {string}
    */
-  code
+  bidsCode
   /**
    * The file associated with this issue.
    * @type {Object}
@@ -17,12 +17,33 @@ export class BidsIssue {
    * The evidence for this issue.
    * @type {string}
    */
-  evidence
+  message
+  /**
+   * The HED Issue object corresponding to this object.
+   * @type {Issue}
+   */
+  hedIssue
 
-  constructor(issueCode, file, evidence) {
-    this.code = issueCode
+  /**
+   * Constructor.
+   *
+   * @param {Issue} hedIssue The HED issue object to be wrapped.
+   * @param {Object} file The file this error occurred in.
+   */
+  constructor(hedIssue, file) {
+    this.hedIssue = hedIssue
+    this.bidsCode = BidsHedIssue._determineBidsIssueCode(hedIssue)
+    this.message = hedIssue.message
     this.file = file
-    this.evidence = evidence
+  }
+
+  /**
+   * The HED spec code for this issue.
+   *
+   * @returns {string}
+   */
+  get hedCode() {
+    return this.hedIssue.hedCode
   }
 
   /**
@@ -30,59 +51,46 @@ export class BidsIssue {
    *
    * @returns {boolean}
    */
-  isError() {
-    return bidsHedErrorCodes.has(this.code)
+  get isError() {
+    return bidsHedErrorCodes.has(this.bidsCode)
   }
 
   /**
    * Determine if any of the passed issues are errors.
    *
-   * @param {BidsIssue[]} issues A list of issues.
+   * @param {BidsHedIssue[]} issues A list of issues.
    * @returns {boolean} Whether any of the passed issues are errors (rather than warnings).
    */
   static anyAreErrors(issues) {
-    return issues.some((issue) => issue.isError())
+    return issues.some((issue) => issue.isError)
   }
 
-  static async generateInternalErrorPromise(error, errorFile) {
-    return [new BidsHedIssue(generateIssue('internalError', { message: error.message }), errorFile)]
-  }
-}
-
-export class BidsHedIssue extends BidsIssue {
   /**
-   * The HED Issue object corresponding to this object.
-   * @type {Issue}
-   */
-  hedIssue
-
-  /**
-   * Constructor.
+   * Generate a {@link Promise} with an internal error.
    *
-   * @param {Issue} hedIssue The HED issue object to be wrapped.
-   * @param {Object} file The file this error occurred in.
+   * @param {string} error The error message.
+   * @param {Object} errorFile The file this error occurred in.
+   * @return {Promise} A promise resolving to a singleton array containing an internal error {@link BidsHedIssue}.
    */
-  constructor(hedIssue, file) {
-    super(BidsHedIssue._determineBidsIssueCode(hedIssue), file, hedIssue.message)
-
-    this.hedIssue = hedIssue
+  static async generateInternalErrorPromise(error, errorFile) {
+    return [new BidsHedIssue(generateIssue('internalError', { message: error.message }), errorFile)]
   }
 
   /**
    * Determine the BIDS issue code for this issue.
    *
    * @param {Issue} hedIssue The HED issue object to be wrapped.
-   * @returns {number} The BIDS issue code for this issue.
+   * @returns {string} The BIDS issue code for this issue.
    * @private
    */
   static _determineBidsIssueCode(hedIssue) {
-    if (hedIssue.internalCode === 'internalError' || hedIssue.internalCode === 'internalConsistencyError') {
-      return 106
+    if (hedIssue.internalCode === 'internalError') {
+      return 'HED_INTERNAL_ERROR'
     }
     if (hedIssue.level === 'warning') {
-      return 105
+      return 'HED_WARNING'
     }
-    return 104
+    return 'HED_ERROR'
   }
 
   /**
diff --git a/src/bids/types/json.js b/src/bids/types/json.js
index 37e8a62a..7e82d73c 100644
--- a/src/bids/types/json.js
+++ b/src/bids/types/json.js
@@ -104,9 +104,9 @@ export class BidsSidecar extends BidsJsonFile {
     } else if (!defManager) {
       this.definitions = new DefinitionManager()
     } else {
-      IssueError.generateAndThrow('internalError', {
-        message: 'Improper format for defManager parameter -- must be null or DefinitionManager',
-      })
+      IssueError.generateAndThrowInternalError(
+        'Improper format for defManager parameter -- must be null or DefinitionManager',
+      )
     }
   }
 
@@ -222,9 +222,7 @@ export class BidsSidecar extends BidsJsonFile {
       } else if (hedData instanceof Map) {
         this._parseCategorySplice(sidecarKey, hedData)
       } else if (hedData) {
-        IssueError.generateAndThrow('internalConsistencyError', {
-          message: 'Unexpected type found in bidsFile parsedHedData map.',
-        })
+        IssueError.generateAndThrowInternalError('Unexpected type found in bidsFile parsedHedData map.')
       }
     }
   }
@@ -250,9 +248,9 @@ export class BidsSidecar extends BidsJsonFile {
 
   /**
    * Add a list of columnSplices to a key map.
-   * @param {Set} keyReferences
+   * @param {Set<string>|null} keyReferences
    * @param {ParsedHedColumnSplice[]} columnSplices
-   * @returns {*|Set<any>}
+   * @returns {Set<string>}
    * @private
    */
   _processColumnSplices(keyReferences, columnSplices) {
@@ -341,13 +339,14 @@ export class BidsSidecarKey {
   }
 
   /**
-   * Parse the value string in a bidsFile
-   * @param {Schemas} hedSchemas - The HED schemas to use.
-   * @returns {Issue[]}
-   * @private
+   * Parse the value string in a bidsFile.
    *
    * ### Note:
    *  The value strings cannot contain definitions.
+   *
+   * @param {Schemas} hedSchemas - The HED schemas to use.
+   * @returns {Issue[]}
+   * @private
    */
   _parseValueString(hedSchemas) {
     const [parsedString, parsingIssues] = parseHedString(this.valueString, hedSchemas, false, true)
diff --git a/src/bids/types/tsv.js b/src/bids/types/tsv.js
index 2a8ce3aa..614bee05 100644
--- a/src/bids/types/tsv.js
+++ b/src/bids/types/tsv.js
@@ -12,7 +12,7 @@ import { IssueError } from '../../issues/issues'
 export class BidsTsvFile extends BidsFile {
   /**
    * This file's parsed TSV data.
-   * @type {Map}
+   * @type {Map<string, string[]>}
    */
   parsedTsv
   /**
@@ -46,7 +46,7 @@ export class BidsTsvFile extends BidsFile {
     } else if (isPlainObject(tsvData)) {
       this.parsedTsv = convertParsedTSVData(tsvData)
     } else {
-      IssueError.generateAndThrow('internalError', { message: 'parsedTsv has an invalid type' })
+      IssueError.generateAndThrowInternalError('parsedTsv has an invalid type')
     }
 
     this.mergedSidecar = new BidsSidecar(name, this.file, mergedDictionary, defManager)
@@ -140,7 +140,7 @@ export class BidsTsvElement {
 
   /**
    * Create a string list of a list of BidsTsvElement objects.
-   * @param BidsTsvElement[] elements - A list of elements to construct line numbers from.
+   * @param {BidsTsvElement[]} elements - A list of elements to construct line numbers from.
    * @returns {string} - A string with the list of line numbers for error messages.
    */
   static getTsvLines(elements) {
diff --git a/src/bids/validator/sidecarValidator.js b/src/bids/validator/sidecarValidator.js
index 097249d3..8f594553 100644
--- a/src/bids/validator/sidecarValidator.js
+++ b/src/bids/validator/sidecarValidator.js
@@ -21,7 +21,7 @@ export class BidsHedSidecarValidator extends BidsValidator {
   /**
    * Validate a BIDS JSON bidsFile file. This method returns the complete issue list for convenience.
    *
-   * @returns {BidsIssue[]} - Any issues found during validation of this bidsFile file.
+   * @returns {BidsHedIssue[]} - Any issues found during validation of this bidsFile file.
    */
   validate() {
     // Allow schema to be set a validation time -- this is checked by the superclass of BIDS file
@@ -40,7 +40,7 @@ export class BidsHedSidecarValidator extends BidsValidator {
   /**
    * Validate this bidsFile's HED strings.
    *
-   * @returns {BidsIssue[]} All issues found.
+   * @returns {BidsHedIssue[]} All issues found.
    */
   _validateStrings() {
     const issues = []
@@ -55,9 +55,7 @@ export class BidsHedSidecarValidator extends BidsValidator {
           issues.push(...this._checkDetails(sidecarKeyName, valueString))
         }
       } else {
-        IssueError.generateAndThrow('internalConsistencyError', {
-          message: 'Unexpected type found in bidsFile parsedHedData map.',
-        })
+        IssueError.generateAndThrowInternalError('Unexpected type found in bidsFile parsedHedData map.')
       }
     }
     return issues
@@ -127,7 +125,7 @@ export class BidsHedSidecarValidator extends BidsValidator {
   /**
    * Validate this bidsFile's curly braces -- checking recursion and missing columns.
    *
-   * @returns {BidsIssue[]} All issues found.
+   * @returns {BidsHedIssue[]} All issues found.
    */
   _validateCurlyBraces() {
     const issues = []
diff --git a/src/bids/validator/tsvValidator.js b/src/bids/validator/tsvValidator.js
index b9b5e2c7..91eac32a 100644
--- a/src/bids/validator/tsvValidator.js
+++ b/src/bids/validator/tsvValidator.js
@@ -1,4 +1,4 @@
-import { BidsHedIssue, BidsIssue } from '../types/issues'
+import { BidsHedIssue } from '../types/issues'
 import { BidsTsvElement, BidsTsvRow } from '../types/tsv'
 import { BidsValidator } from './validator'
 import { parseHedString } from '../../parser/parser'
@@ -32,14 +32,14 @@ export class BidsHedTsvValidator extends BidsValidator {
   /**
    * Validate a BIDS TSV file. This method returns the complete issue list for convenience.
    *
-   * @returns {BidsIssue[]} - Any issues found during validation of this TSV file.
+   * @returns {BidsHedIssue[]} - Any issues found during validation of this TSV file.
    */
   validate() {
     // Validate the BIDS bidsFile if it exists.
     if (this.bidsFile.mergedSidecar) {
       const sidecarIssues = this.bidsFile.mergedSidecar.validate(this.hedSchemas)
       this.issues.push(...sidecarIssues)
-      if (BidsIssue.anyAreErrors(sidecarIssues)) {
+      if (BidsHedIssue.anyAreErrors(sidecarIssues)) {
         return this.issues
       }
     }
@@ -47,14 +47,14 @@ export class BidsHedTsvValidator extends BidsValidator {
     // Valid the HED column by itself.
     const hedColumnIssues = this._validateHedColumn()
     this.issues.push(...hedColumnIssues)
-    if (BidsIssue.anyAreErrors(this.issues)) {
+    if (BidsHedIssue.anyAreErrors(this.issues)) {
       return this.issues
     }
     // Now do a full validation
     const bidsHedTsvParser = new BidsHedTsvParser(this.bidsFile, this.hedSchemas)
     const [bidsEvents, parsingIssues] = bidsHedTsvParser.parse()
     this.issues.push(...parsingIssues)
-    if (!BidsIssue.anyAreErrors(this.issues)) {
+    if (!BidsHedIssue.anyAreErrors(this.issues)) {
       this.issues.push(...this.validateDataset(bidsEvents))
     }
     return this.issues
@@ -63,7 +63,7 @@ export class BidsHedTsvValidator extends BidsValidator {
   /**
    * Validate this TSV file's HED column.
    *
-   * @returns {BidsIssue[]} - Issues found in validating the HED column without sidecar information.
+   * @returns {BidsHedIssue[]} - Issues found in validating the HED column without sidecar information.
    * @private
    */
   _validateHedColumn() {
@@ -80,7 +80,7 @@ export class BidsHedTsvValidator extends BidsValidator {
    *
    * @param {string} hedString - The string to be validated.
    * @param {number} rowIndex - The index of this row in the TSV file.
-   * @returns {BidsIssue[]} - Specific issues found in validating the HED column
+   * @returns {BidsHedIssue[]} - Specific issues found in validating the HED column
    * @private
    */
   _validateHedColumnString(hedString, rowIndex) {
@@ -165,13 +165,13 @@ export class BidsHedTsvValidator extends BidsValidator {
   /**
    * Check for duplicate tags when multiple rows with the same onset.
    *
-   * @param {BidsTsvElement[]} elements - The elements representing the tsv file.
-   * @returns {BidsHedIssue[]} - Errors in temporal relationships among events.
-   * @private
-   *
    * ### Note:
    * Duplicate onsets are relatively rare and duplicates for single rows are checked when a ParsedHedString is
    * constructed.
+   *
+   * @param {BidsTsvElement[]} elements - The elements representing the tsv file.
+   * @returns {BidsHedIssue[]} - Errors in temporal relationships among events.
+   * @private
    */
   _checkDuplicatesAcrossRows(elements) {
     const duplicateMap = this._getOnsetMap(elements)
diff --git a/src/bids/validator/validator.js b/src/bids/validator/validator.js
index fcd77332..18ac2713 100644
--- a/src/bids/validator/validator.js
+++ b/src/bids/validator/validator.js
@@ -14,7 +14,7 @@ export class BidsValidator {
   hedSchemas
   /**
    * The issues found during validation.
-   * @type {BidsIssue[]}
+   * @type {BidsHedIssue[]}
    */
   issues
 
@@ -33,7 +33,7 @@ export class BidsValidator {
   /**
    * Validate a BIDS TSV file. This method returns the complete issue list for convenience.
    *
-   * @returns {BidsIssue[]} - Any issues found during validation of this TSV file.
+   * @returns {BidsHedIssue[]} - Any issues found during validation of this TSV file.
    */
   validate() {
     return this.issues
diff --git a/src/issues/data.js b/src/issues/data.js
index 4d7f19d7..9dce777d 100644
--- a/src/issues/data.js
+++ b/src/issues/data.js
@@ -475,13 +475,8 @@ export default {
     message: stringTemplate`Unknown HED error "${'internalCode'}" - parameters: "${'parameters'}".`,
   },
   internalError: {
-    hedCode: 'GENERIC_ERROR',
+    hedCode: 'INTERNAL_ERROR',
     level: 'error',
     message: stringTemplate`Internal error - message: "${'message'}".`,
   },
-  internalConsistencyError: {
-    hedCode: 'GENERIC_ERROR',
-    level: 'error',
-    message: stringTemplate`Internal consistency error - message: "${'message'}".`,
-  },
 }
diff --git a/src/issues/issues.js b/src/issues/issues.js
index 0edb9382..36b5c1b0 100644
--- a/src/issues/issues.js
+++ b/src/issues/issues.js
@@ -9,9 +9,15 @@ export class IssueError extends Error {
    */
   issue
 
+  /**
+   * Constructor.
+   *
+   * @param {Issue} issue The associated HED issue.
+   * @param {...*} params Extra parameters (to be forwarded to the {@link Error} constructor).
+   */
   constructor(issue, ...params) {
     // Pass remaining arguments (including vendor specific ones) to parent constructor
-    super(...params)
+    super(issue.message, ...params)
 
     // Maintains proper stack trace for where our error was thrown (only available on V8)
     if (Error.captureStackTrace) {
@@ -20,7 +26,6 @@ export class IssueError extends Error {
 
     this.name = 'IssueError'
     this.issue = issue
-    this.message = issue.message
 
     Object.setPrototypeOf(this, IssueError.prototype)
   }
@@ -35,6 +40,16 @@ export class IssueError extends Error {
   static generateAndThrow(internalCode, parameters = {}) {
     throw new IssueError(generateIssue(internalCode, parameters))
   }
+
+  /**
+   * Generate a new {@link Issue} object for an internal error and immediately throw it as an {@link IssueError}.
+   *
+   * @param {string} message A message describing the internal error.
+   * @throws {IssueError} Corresponding to the generated internal error {@link Issue}.
+   */
+  static generateAndThrowInternalError(message = 'Unknown internal error') {
+    throw new IssueError(generateIssue('internalError', { message }))
+  }
 }
 
 /**
@@ -88,7 +103,7 @@ export class Issue {
    *
    * @returns {boolean}
    */
-  isError() {
+  get isError() {
     return this.level === 'error'
   }
 
@@ -137,7 +152,7 @@ export class Issue {
    * @returns {Array} Returns [boolean, Issue[]] indicate if validation succeeded (i.e. any errors were found)and all issues (both errors and warnings).
    */
   static issueListWithValidStatus(issues) {
-    return [!issues.some((issue) => issue.isError()), issues]
+    return [!issues.some((issue) => issue.isError), issues]
   }
 }
 
diff --git a/src/parser/reservedChecker.js b/src/parser/reservedChecker.js
index 1d8d6fa5..b0a4f635 100644
--- a/src/parser/reservedChecker.js
+++ b/src/parser/reservedChecker.js
@@ -1,5 +1,5 @@
 import reservedTags from '../data/json/reservedTags.json'
-import { generateIssue } from '../issues/issues'
+import { generateIssue, IssueError } from '../issues/issues'
 import { getTagListString } from './parseUtils'
 
 export class ReservedChecker {
@@ -8,7 +8,7 @@ export class ReservedChecker {
 
   constructor() {
     if (ReservedChecker.instance) {
-      throw new Error('Use ReservedChecker.getInstance() to get an instance of this class.')
+      IssueError.generateAndThrowInternalError('Use ReservedChecker.getInstance() to get an instance of this class.')
     }
 
     this._initializeReservedTags()
diff --git a/src/schema/containers.js b/src/schema/containers.js
index a90d6331..d2e4c415 100644
--- a/src/schema/containers.js
+++ b/src/schema/containers.js
@@ -1,3 +1,4 @@
+import { IssueError } from '../issues/issues'
 import { getGenerationForSchemaVersion } from '../utils/hedData'
 
 /**
@@ -122,7 +123,7 @@ export class Schemas {
     } else if (schemas instanceof Schema) {
       this.schemas = new Map([['', schemas]])
     } else {
-      throw new Error('Invalid type passed to Schemas constructor')
+      IssueError.generateAndThrowInternalError('Invalid type passed to Schemas constructor')
     }
     if (this.schemas) {
       this._addNicknamesToSchemas()
diff --git a/src/schema/entries.js b/src/schema/entries.js
index f94ae80c..22a7f818 100644
--- a/src/schema/entries.js
+++ b/src/schema/entries.js
@@ -181,7 +181,7 @@ export class SchemaEntryManager extends Memoizer {
    */
   getEntriesWithBooleanAttribute(booleanAttributeName) {
     return this._memoize(booleanAttributeName, () => {
-      return this.filter(([_, v]) => {
+      return this.filter(([, v]) => {
         return v.hasAttributeName(booleanAttributeName)
       })
     })
@@ -783,7 +783,7 @@ export class SchemaTag extends SchemaEntryWithAttributes {
    * @type {SchemaTag}
    * @private
    */
-  _parent
+  #parent
   /**
    * This tag's unit classes.
    * @type {SchemaUnitClass[]}
@@ -803,7 +803,7 @@ export class SchemaTag extends SchemaEntryWithAttributes {
    * @type {SchemaValueTag}
    * @private
    */
-  _valueTag
+  #valueTag
 
   /**
    * Constructor.
@@ -858,7 +858,7 @@ export class SchemaTag extends SchemaEntryWithAttributes {
    * @returns {SchemaValueTag}
    */
   get valueTag() {
-    return this._valueTag
+    return this.#valueTag
   }
 
   /**
@@ -866,12 +866,8 @@ export class SchemaTag extends SchemaEntryWithAttributes {
    * @param {SchemaValueTag} newValueTag The new value-taking child tag.
    */
   set valueTag(newValueTag) {
-    if (this._valueTag === undefined) {
-      this._valueTag = newValueTag
-    } else {
-      IssueError.generateAndThrow('internalError', {
-        message: `Attempted to set value tag for schema tag "${this.longName}" when it already has one.`,
-      })
+    if (!this.#isPrivateFieldSet(this.#valueTag, 'value tag')) {
+      this.#valueTag = newValueTag
     }
   }
 
@@ -880,7 +876,7 @@ export class SchemaTag extends SchemaEntryWithAttributes {
    * @type {SchemaTag}
    */
   get parent() {
-    return this._parent
+    return this.#parent
   }
 
   /**
@@ -888,13 +884,27 @@ export class SchemaTag extends SchemaEntryWithAttributes {
    * @param {SchemaTag} newParent The new parent tag.
    */
   set parent(newParent) {
-    if (this._parent === undefined) {
-      this._parent = newParent
-    } else {
-      IssueError.generateAndThrow('internalError', {
-        message: `Attempted to set parent for schema tag ${this.longName} when it already has one.`,
-      })
+    if (!this.#isPrivateFieldSet(this.#parent, 'parent')) {
+      this.#parent = newParent
+    }
+  }
+
+  /**
+   * Throw an error if a private field is already set.
+   *
+   * @param {*} field The field being set.
+   * @param {string} fieldName The name of the field (for error reporting).
+   * @return {boolean} Whether the field is set (never returns true).
+   * @throws {IssueError} If the field is already set.
+   * @private
+   */
+  #isPrivateFieldSet(field, fieldName) {
+    if (field !== undefined) {
+      IssueError.generateAndThrowInternalError(
+        `Attempted to set ${fieldName} for schema tag ${this.longName} when it already has one.`,
+      )
     }
+    return false
   }
 
   /**
diff --git a/src/schema/schemaMerger.js b/src/schema/schemaMerger.js
index 79d4c29f..13056f25 100644
--- a/src/schema/schemaMerger.js
+++ b/src/schema/schemaMerger.js
@@ -36,7 +36,7 @@ export default class PartneredSchemaMerger {
    */
   _validate() {
     if (!this.sourceSchemas.every((schema) => schema.generation === 3)) {
-      IssueError.generateAndThrow('internalConsistencyError', { message: 'Partnered schemas must be HED-3G schemas' })
+      IssueError.generateAndThrowInternalError('Partnered schemas must be HED-3G schemas')
     }
 
     for (const schema of this.sourceSchemas.slice(1)) {
@@ -118,7 +118,7 @@ export default class PartneredSchemaMerger {
     if (rootedTagShortName) {
       const parentTag = tag.parent
       if (parentTag?.name?.toLowerCase() !== rootedTagShortName?.toLowerCase()) {
-        IssueError.generateAndThrow('internalError', { message: `Node ${shortName} is improperly rooted.` })
+        IssueError.generateAndThrowInternalError(`Node ${shortName} is improperly rooted.`)
       }
     }
 
diff --git a/src/utils/files.js b/src/utils/files.js
index 37a07092..0665ee88 100644
--- a/src/utils/files.js
+++ b/src/utils/files.js
@@ -2,6 +2,8 @@ import fs from 'fs'
 
 import fetch from 'cross-fetch'
 
+import { IssueError } from '../issues/issues'
+
 /**
  * Read a local file.
  *
@@ -29,7 +31,9 @@ export function readFile(fileName) {
 export async function readHTTPSFile(url) {
   const response = await fetch(url)
   if (!response.ok) {
-    throw new Error(`Server responded to ${url} with status code ${response.status}: ${response.statusText}`)
+    IssueError.generateAndThrowInternalError(
+      `Server responded to ${url} with status code ${response.status}: ${response.statusText}`,
+    )
   }
   return response.text()
 }
diff --git a/src/utils/memoizer.js b/src/utils/memoizer.js
index b576042b..19b6d70e 100644
--- a/src/utils/memoizer.js
+++ b/src/utils/memoizer.js
@@ -32,9 +32,7 @@ export default class Memoizer {
    */
   _memoize(propertyName, valueComputer) {
     if (!propertyName) {
-      IssueError.generateAndThrow('internalConsistencyError', {
-        message: 'Invalid property name in Memoizer subclass.',
-      })
+      IssueError.generateAndThrowInternalError('Invalid property name in Memoizer subclass.')
     }
     if (this._memoizedProperties.has(propertyName)) {
       return this._memoizedProperties.get(propertyName)