I've been investigating this for a while now, and I believe it has stopped happening, but I do not know why. Things that are different in the code I switched from using a std::packaged_task to simply using a std::function My packaged_task actually spawned more worker threads - (that is what appears to be the trigger for the above crash log) - it now does not maybe at the cost of some performance... maybe Normally I'd just say I'm bad at multithreaded programming and give up, but the fact that it is ONLY happening on iOS 15.4 makes me wonder if there was some sort of threading policy change.

Update #2: Not it hasn't stopped happening :\

Same issue here, wasn't a problem a month or so ago.

In the same boat. Submitted the app and the subscription for review (is there any way to "connect them"?) - The app was actually rejected because they couldn't find the subscription because of a server config issue. Fixed the issue and the app was approved. I foolishly assumed that the subscription was approved. It was rejected but with no reason given. Made some random changes and resubmitted, hoping for the best. I talked to the expedite team and they said that a different team handles the IAP/subscription approvals. I think this structure may be the reason for the headache. Part of the purpose of app review is to make sure customers can access the subscription and it is not deceptive. Unfortunately it seems like this process has led many to provide a confusing customer experience. Hope we can see this out-of-sync issue fixed in the near future.

Here in 9/2023, this was simply a Cocoa pods bug for Archiving. sudo gem update cocoapods then do all the things.