Philips Hue switches become inaccessible

This happened twice so far and I’m not sure how to diagnose and fix the issue. After reboots, both of my RWL021 switches have become inaccessible in ZHA (both at different times). Only way I found to fix one was to delete it and repair it. Every single other attempt (reconfigure, repair only without deleting) failed. Also resetting the switch (without repairing) throws somekind of angry error message on the switch. I have a Sonoff espz zigbee dongle.

Any suggestions to diagnose the zigbee issue?