Bump! We are experience the same problems on different iOS (14.2, 14.1, 14.3, 14.4, 13.7, 13.6) Never managed to catch this exception in debug. The only thing we've noticed that app was in a background for a while before that, so this could happens after the app goes foreground. We still not sure about that.

This solution kind of works, but it's stopped working in some cases in release builds. I have an accesoryInputView in the main controller and the search controller which appears after the long tap on the navigation bar (it's searching messages in chat like Telegram does). So, this solution works well on iOS < 15.1 and also on all debug builds. But when it comes to release-scheme build – search bar occasionally may be dismissed with a parent view controller. It's so weird, because now I need hacky solution over the hacky solution. I would expect some fix for this issue from Apple but right now issue only become more complicated =)