Thanks Aiiboo, following your directions I was able to upload to AppStoreConnect.

Hi, we've had the very same problem on an App that we inherited. After recompiling under Xcode 12 we started having this very same error every time there was a call to a moc. Ended with encaplusated every call in performBlock or performBlockAndWait fixed our problem. Hope this helps somebody.

Hello, thanks for your feedback. I've submitted a bug report as suggested, here's the FB number: FB15590204