Update:
Today I Found another way to fix one.
It was a Aqara Vibration sensor not reacting anymore, showing a bad route [?] in the Developer Tools - ZigBee
After starting an Interview I started Pressing the button short on the device every ~3 seconds.
These Devices have a lot of capabilities so need a lot presses before a complete interview is done but I guess after a couple of Presses it already was back in the network.
Fixed!