As for Xiaomi Sensors I can say that they lose connection when they lose their parent. So maybe that is the case here. For other connection issues please make sure you have a 5.1V power supply if you have a RPI4 and there are no USB peripherals that can cause interferences. Unplug them for testing if necessary.
Another trick is to reboot the RaspBee2 FW with the console command sudo GCFFlasher_internal -r if you have access to the RPI console.