diff --git a/.github/buildomat/build-and-test.sh b/.github/buildomat/build-and-test.sh
index 6cf7f578fb1..0ae5c0ddc84 100755
--- a/.github/buildomat/build-and-test.sh
+++ b/.github/buildomat/build-and-test.sh
@@ -128,9 +128,13 @@ ptime -m cargo build -Z unstable-options --timings=json \
 #
 # We apply our own timeout to ensure that we get a normal failure on timeout
 # rather than a buildomat timeout.  See oxidecomputer/buildomat#8.
-#
+# To avoid too many tests running at the same time, we choose a test threads
+# 2 less (negative 2) than the default.  This avoids many test flakes where
+# the test would have worked but the system was too overloaded and tests
+# take longer than their default timeouts.
 banner test
-ptime -m timeout 2h cargo nextest run --profile ci --locked --verbose
+ptime -m timeout 2h cargo nextest run --profile ci --locked --verbose \
+    --test-threads -2
 
 #
 # https://github.com/nextest-rs/nextest/issues/16
diff --git a/nexus/src/app/background/tasks/instance_reincarnation.rs b/nexus/src/app/background/tasks/instance_reincarnation.rs
index acc7b302be7..7858676891f 100644
--- a/nexus/src/app/background/tasks/instance_reincarnation.rs
+++ b/nexus/src/app/background/tasks/instance_reincarnation.rs
@@ -910,8 +910,10 @@ mod test {
         .await;
 
         // Activate the background task again. Now, only instance 2 should be
-        // restarted.
+        // restarted.  Possible test flake here and this adds a bit more debug
+        // if we see this assertion fail.
         let status = assert_activation_ok!(task.activate(&opctx).await);
+        eprintln!("status: {:?}", status);
         assert_eq!(status.total_instances_found(), 1);
         assert_eq!(
             status.instances_reincarnated,
diff --git a/nexus/src/app/sagas/region_snapshot_replacement_start.rs b/nexus/src/app/sagas/region_snapshot_replacement_start.rs
index c047b56479d..d3cf05af796 100644
--- a/nexus/src/app/sagas/region_snapshot_replacement_start.rs
+++ b/nexus/src/app/sagas/region_snapshot_replacement_start.rs
@@ -1534,17 +1534,21 @@ pub(crate) mod test {
         request: &RegionSnapshotReplacement,
     ) {
         let opctx = test_opctx(cptestctx);
+
         let db_request = datastore
             .get_region_snapshot_replacement_request_by_id(&opctx, request.id)
             .await
             .unwrap();
 
         assert_eq!(db_request.new_region_id, None);
-        assert_eq!(
-            db_request.replacement_state,
-            RegionSnapshotReplacementState::Requested
-        );
         assert_eq!(db_request.operating_saga_id, None);
+
+        match db_request.replacement_state {
+            RegionSnapshotReplacementState::Requested => {}
+            x => {
+                panic!("replacement state {:?} != Requested", x);
+            }
+        }
     }
 
     async fn assert_volume_untouched(
diff --git a/nexus/test-utils/src/resource_helpers.rs b/nexus/test-utils/src/resource_helpers.rs
index 3b713705b63..71871e932c8 100644
--- a/nexus/test-utils/src/resource_helpers.rs
+++ b/nexus/test-utils/src/resource_helpers.rs
@@ -1688,7 +1688,7 @@ impl<'a, N: NexusServer> DiskTest<'a, N> {
                 }
             },
             &Duration::from_millis(50),
-            &Duration::from_secs(30),
+            &Duration::from_secs(120),
         )
         .await
         .expect("expected to find inventory collection");
diff --git a/nexus/tests/integration_tests/crucible_replacements.rs b/nexus/tests/integration_tests/crucible_replacements.rs
index 8e17d851992..efc87e503ec 100644
--- a/nexus/tests/integration_tests/crucible_replacements.rs
+++ b/nexus/tests/integration_tests/crucible_replacements.rs
@@ -202,7 +202,7 @@ pub(crate) async fn wait_for_all_replacements(
             }
         },
         &std::time::Duration::from_millis(50),
-        &std::time::Duration::from_secs(180),
+        &std::time::Duration::from_secs(260),
     )
     .await
     .expect("all replacements finished");
@@ -480,7 +480,7 @@ mod region_replacement {
                     }
                 },
                 &std::time::Duration::from_millis(50),
-                &std::time::Duration::from_secs(60),
+                &std::time::Duration::from_secs(260),
             )
             .await
             .expect("request transitioned to expected state");
@@ -1070,24 +1070,34 @@ async fn test_racing_replacements_for_soft_deleted_disk_volume(
         activate_background_task(&internal_client, "region_replacement_driver")
             .await;
 
-    assert!(match last_background_task.last {
+    let res = match last_background_task.last {
         LastResult::Completed(last_result_completed) => {
             match serde_json::from_value::<RegionReplacementDriverStatus>(
                 last_result_completed.details,
             ) {
                 Err(e) => {
+                    eprintln!("Json not what we expected");
                     eprintln!("{e}");
                     false
                 }
 
-                Ok(v) => !v.drive_invoked_ok.is_empty(),
+                Ok(v) => {
+                    if !v.drive_invoked_ok.is_empty() {
+                        eprintln!("v.drive_ok: {:?}", v.drive_invoked_ok);
+                        true
+                    } else {
+                        eprintln!("v.drive_ok: {:?} empty", v.drive_invoked_ok);
+                        false
+                    }
+                }
             }
         }
-
-        _ => {
+        x => {
+            eprintln!("Unexpected result here: {:?}", x);
             false
         }
-    });
+    };
+    assert!(res);
 
     // wait for the drive saga to complete here
     wait_for_condition(
@@ -1484,20 +1494,33 @@ mod region_snapshot_replacement {
 
             // Assert no volumes are referencing the snapshot address
 
-            let volumes = self
-                .datastore
-                .find_volumes_referencing_socket_addr(
-                    &self.opctx(),
-                    self.snapshot_socket_addr,
-                )
-                .await
-                .unwrap();
+            let mut counter = 1;
+            loop {
+                let volumes = self
+                    .datastore
+                    .find_volumes_referencing_socket_addr(
+                        &self.opctx(),
+                        self.snapshot_socket_addr,
+                    )
+                    .await
+                    .unwrap();
 
-            if !volumes.is_empty() {
-                eprintln!("{:?}", volumes);
+                if !volumes.is_empty() {
+                    eprintln!(
+                        "Volume should be gone, try {counter} {:?}",
+                        volumes
+                    );
+                    tokio::time::sleep(std::time::Duration::from_secs(5)).await;
+                    counter += 1;
+                    if counter > 200 {
+                        panic!(
+                            "Tried 200 times, and still this did not finish"
+                        );
+                    }
+                } else {
+                    break;
+                }
             }
-
-            assert!(volumes.is_empty());
         }
 
         /// Assert no Crucible resources are leaked
@@ -1648,32 +1671,59 @@ mod region_snapshot_replacement {
             match result {
                 InsertStepResult::Inserted { .. } => {}
 
-                _ => {
-                    assert!(
-                        false,
-                        "bad result from create_region_snapshot_replacement_step"
+                InsertStepResult::AlreadyHandled { existing_step_id } => {
+                    let region_snapshot_replace_request = self
+                        .datastore
+                        .get_region_snapshot_replacement_request_by_id(
+                            &self.opctx(),
+                            existing_step_id,
+                        )
+                        .await;
+                    eprintln!(
+                        "we were suppose to create this: {:?} but found it AlreadyHandled, then got {:?}",
+                        self.replacement_request_id,
+                        region_snapshot_replace_request
                     );
+                    panic!("Something else created our replacement");
                 }
             }
         }
 
         pub async fn assert_read_only_target_gone(&self) {
-            let region_snapshot_replace_request = self
-                .datastore
-                .get_region_snapshot_replacement_request_by_id(
-                    &self.opctx(),
-                    self.replacement_request_id,
-                )
-                .await
-                .unwrap();
+            eprintln!(
+                "Starting, replace_request_id: {:?}",
+                self.replacement_request_id
+            );
+            let mut i = 1;
+            loop {
+                let region_snapshot_replace_request = self
+                    .datastore
+                    .get_region_snapshot_replacement_request_by_id(
+                        &self.opctx(),
+                        self.replacement_request_id,
+                    )
+                    .await
+                    .unwrap();
+                eprintln!(
+                    "In loop {i} with rs_replace_request: {:?}",
+                    region_snapshot_replace_request
+                );
 
-            assert!(
-                self.datastore
+                let res = self
+                    .datastore
                     .read_only_target_addr(&region_snapshot_replace_request)
                     .await
-                    .unwrap()
-                    .is_none()
-            );
+                    .unwrap();
+
+                eprintln!("In loop {i} target that should be gone: {:?}", res);
+                if res.is_none() {
+                    // test pass, move on
+                    break;
+                }
+                eprintln!("loop {i}, snapshot that should be gone: {:?}", res);
+                tokio::time::sleep(std::time::Duration::from_secs(5)).await;
+                i += 1;
+            }
         }
 
         pub async fn remove_disk_from_snapshot_rop(&self) {
diff --git a/nexus/tests/integration_tests/instances.rs b/nexus/tests/integration_tests/instances.rs
index 7de9e892a0b..9b7a7ecc24e 100644
--- a/nexus/tests/integration_tests/instances.rs
+++ b/nexus/tests/integration_tests/instances.rs
@@ -7656,7 +7656,7 @@ pub async fn instance_wait_for_state_as(
     instance_id: InstanceUuid,
     state: omicron_common::api::external::InstanceState,
 ) -> Instance {
-    const MAX_WAIT: Duration = Duration::from_secs(120);
+    const MAX_WAIT: Duration = Duration::from_secs(320);
 
     slog::info!(
         &client.client_log,
diff --git a/sled-agent/src/sim/http_entrypoints_pantry.rs b/sled-agent/src/sim/http_entrypoints_pantry.rs
index 672f36d1207..0955aaa4dff 100644
--- a/sled-agent/src/sim/http_entrypoints_pantry.rs
+++ b/sled-agent/src/sim/http_entrypoints_pantry.rs
@@ -399,8 +399,18 @@ mod tests {
         let raw_url = format!(
             "https://raw.githubusercontent.com/oxidecomputer/crucible/{part}/openapi/crucible-pantry.json",
         );
-        let raw_json =
-            reqwest::blocking::get(&raw_url).unwrap().text().unwrap();
+
+        // The default timeout of 30 seconds was sometimes not enough
+        // heavy load.
+        let raw_json = reqwest::blocking::Client::builder()
+            .timeout(std::time::Duration::from_secs(120))
+            .build()
+            .unwrap()
+            .get(&raw_url)
+            .send()
+            .unwrap()
+            .text()
+            .unwrap();
         serde_json::from_str(&raw_json).unwrap()
     }