App quits right after launching

Since iOS 14, more and more users experience a severe problem: When they launch our app, it quits right after showing the launch screen, obviously even before executing one line of code.
In some cases, offloading and re-loading the app can help in this situation, but not always. In iOS 13, the problem occurred in the same way, but offloading and re-loading always helped.
This seems to be a licence problem and reinstalling is no option, because our app holds critical personal data that the user often did not backup. So what can we do in this situation?

App quits right after launching
 
 
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