Both webschemas.org and schema.org (sdo-deimos / master codebase) give an HTTP 500 error to W3C's validator:
@RichardWallis can you have a look?
Fixes for 3.0
Fix for (#1157) 500 Error served to W3C Validator
Potential fix for old version being cached after deployment - set max-age to 10mins
Added creation of jsonldcontext to warmup processing
Removed Excessive debug output
Hot-fixes around caching, validation and 'manufacturer' property.
See #1159 #1157
Fixed in V3.0