I don’t know what the problem is, but I doubt that one device can slow down z2m. I personally never experience this and have 80+ zigbee devices. It most likely some problem with a coordinator or z2m config.
Can it possibly have something to do with the recent ha update to 2023.10.2? Something with ingress to the z2m container? It’s so weird that it never happened this way before and nothing really changed. Also as it seems that it does not affect the functionality (not I can notice at least)…
Edit: I resetted that one device and that logging is now gone, but the issue persists…
Hello, I had same issue with Zigbee2MQTT UI. I got all the readings from my sensors, so I didn’t notice that one of my automation does not work until my wife told me (light toggle based on motion sensors). After reading your post I revert back to: core_2023.10.0 and everything works again.
BTW: DO NOT FORGET to create a new backup of your current setup if you changed something between updates