I tried your suggestion. All worked fine until now.
Now I received the same error message like in the first message of this thread:
Die Remoteverbindung mit dem Gerät wurde unterbrochen...
Completely the same behavior: Debugger is closed and display program hungs.
COM-Port and network communication was active/opend but not used at the moment the interrupt occurred.
I'm not wondering because the network connection was interrupted also with my first posts.
I have also to mention, that network interrupts also occur in release mode (without use of USB).