3 second delays in 'Friends of Hue' -> Conbee -> Zigbee2MQTT

I have a couple of ‘Friends of Hue’ switches and I started experiencing delays of several seconds between using the switch and the light reacting.

My Setup:

  • 4 double FoH switches
  • Several other switches of different brands
  • Lights, sensors etc. of several different brands
  • ConBee II zigbee coordinator
  • Homeassistant running in supervised mode on 5.10.0-14-amd64 #1 SMP Debian 5.10.113-1 (2022-04-29) x86_64
  • Zigbee2MQTT HA add-on
  • Mosquitto HA add-on

All other Zigbee devices seem to react normally at the moment.

After looking at the MQTT-traffic I found that when I press and release e.g. button 1 on the switch, the message with ‘release_1’ gets sent immediately, while ‘press_1’ is almost invariably 3 whole seconds later! On some rare occasions it is even 6 seconds late and in even rarer instances both messages arrive on time and in the right order.

This whole setup has been working flawlessly for month until a few days ago this strange behaviour started. I am not entirely sure but I may have updated Zigbee2MQTT around that time. I am quite sure I did not change anything else, particularly not in the Zigbee network.

A possible scenario that would explain this behaviour is that somewhere in the chain switch-(Zigbee router?)-coordinator-Zigbee2MQTT-Mosquitto the first message gets buffered for 3 seconds because the downstream connection needs to established first. And when the second message arrives, the connection is setup and the message goes through without delay.

Anyone who can shed a light on this?