Repro:

1. Open levels/L0A in the attached 'CanvasCrashRepro.zip'.
2. Enable 'Canvas' object in hierarchy, Unity should crash.
3. Reopen the project, disable 'enemyBlockade', enable 'Canvas', enable 'enemyBlockade', no crash.
4. Crash only happens if 16 or more 'largeVirus' objects are enabled. If canvas components are removed, the crash no longer happens.
5. Moving the child objects to root, so that 'healthDisplay' objects are directly in hierarchy has no effect, the crash still happens as long as there already atleast 16 enabled canvasses in the scene when enabling 'Canvas', but not the other way around.

I'm pretty sure that this must somehow be related to 620511, but the crash here is only triggered by enabling the object with canvas and not by it being present in the scene also the stack trace seems to be different.

Not really sure whether this is actually a regression, but it doesn't crash on b7.