SubApp crashes main app

I use a modal SubApp to pause my game, giving the player these options:
1: Continue
2: Restart current stage (forces main app to restart current frame)
3: Quit current stage (forces main app to jump to a different frame)

When the SubApp ends and the player has chosen option 2 or 3 the whole game crashes when restarting or changing the frame. Also happens if the SubApp is not modal.

First I thought about a timing problem, but it doesn't matter if I wait some seconds after destroying the finished SubApp or if I don't destroy it at all.

Edit: I noticed the same technique still works in my older games, which are Windows only. My current game is for iOS and Windows, I just set a flag and the app executes runtime-specific events. So, does the iOS stuff cause problems in the Windows runtime? This game is quite complex and there are zero problems, only the SubApp is somehow involved.

I tried to find out if a single iOS-related Object causes the problem and yes, it's the Chartboost extension. Once I remove it from the frame (really delete the Object, not just a destroy event!) everything works fine. I'll tell the developer about this issue.