Getting this too with an external dependency. Seems like this warning's been promoted to a failure as of b4. Can anyone provide some insight as to how to revert it to just a warning again?

Just seconding this. We're seeing the same thing on iOS 14 devices on the version we just shipped built against the 14 SDK.

Wonder if it's worth throwing together a radarr for this so it gets attention. For what it's worth I don't see many of these so far and no repeats for users, they typically occur after a period of inactivity that could be foreground or background. Impact-wise I'm a little less concerned.

Have submitted a radar. Adding more information in the hopes we can get a response. We've got a number of other CoreData related crashes impacting the subset of our users on the new version built against the 14 SDK and running iOS 14. Trace below. Other code executing at the same time is random, no consistency. Timing of crash is random. Our evaluation is that we're seeing a regression in CoreData on iOS 14. Crashed: NSManagedObjectContext 0x281a80410 0	CoreData											 0x18919bcf4 -[NSManagedObjectContext _disposeObjects:count:notifyParent:] + 224 1	CoreData											 0x189191f4c -[NSManagedObjectContext _dispose:] + 324 2	CoreData											 0x18907f384 -[NSManagedObjectContext _dealloc__] + 472 3	CoreData											 0x1891a6b74 __internalBlockToDeallocNSManagedObjectContext_block_invoke + 52 4	CoreData											 0x189199b18 developerSubmittedBlockToNSManagedObjectContextPerform + 156 5	libdispatch.dylib							0x182f8b280 _dispatch_client_callout + 16 6	libdispatch.dylib							0x182f33fa8 _dispatch_lane_serial_drain$VARIANT$mp + 612 7	libdispatch.dylib							0x182f34a84 _dispatch_lane_invoke$VARIANT$mp + 424 8	libdispatch.dylib							0x182f3e518 _dispatch_workloop_worker_thread + 712 9	libsystem_pthread.dylib				0x1c7f985a4 _pthread_wqthread + 272 10 libsystem_pthread.dylib				0x1c7f9b874 start_wqthread + 8

Debugging with the flag provided by engineer above helped us quickly isolate areas of concern. This makes a lot of sense. Massive thanks for the comprehensive explanation.

This is still a problem in b5. Are there any updates on this issue?

Thread here https://developer.apple.com/forums/thread/682285?page=1#684322022

An update. As per other suggestions updating to 13.2 RC resolved. This isn’t ideal.

We've discovered this overnight. It's seriously impacting us, issue seems to be having the number be optional. Broken key functionality in our widely used app. Really unnerving a regression like this can happen in a minor iOS release.