for me that happened because of interference. I switched from a Conbee II to a Sonoff Dongle-P and that already helped tremendously. That new dongle is way more stable for me. Also I changed my wifi and Zigbee channels and reduced the transmit power for less interference. Since than my Zigbee netwerk is really stable.
Updating the firmware in my sonoff dongle-p made a massive difference in network stability. It's a bit of a mission to get the update installed but was well worth it.
