iOS 14 Error APSTopicListOpportunistic and SIGKILL on background

On my iOS 14 Beta 3 device: I noticed that the TestFlight variant shows on device wakeup randomly the popup "App <my-app> has crashed, send log?". The app uses geofence in background so I tried to debug with Xcode 11, original source code and linked Device Support Files on the device. But each time I bring the app in the background via app switcher, the app is instantly get killed by the os. The device logs showed me the error

Unable to move topic com.example.my-app, This topic was not in the list provided! APSTopicListOpportunistic

I didn't find any results about APSTopicListOpportunistic, does anybody know something about this error? It seems to be related to APNS (by naming), but push notifications work fine and the moment is a bit confusing.

But also warnings about file handles get instantly removed and access to them results in

not an SQLite database: /var/mobile/Containers/Shared/AppGroup/3EAA8534-A594-4852-824B-D2D45C91D80B/default.realm

So I commented out all code in applicationDidEnterBackground that previously invalidated timers, read a value from the realm database and stopped websocket connections. The errors are gone, but the debugger tells that the app gets still killed instantly

Terminated due to signal 9

If it helps applicationWillTerminate is not being called.

On iOS 13 the app was still active in background (verified via debugger), and I could reopen it to wake it up. Now it always gets cold-restarted.

Thanks for your help or if you experience the same issues. Unfortunately I couldn't test if it also occured in previous iOS Beta versions.