Just a thought, and not making any recommendations (but wanted to share an experience regarding failing Zigbee devices). Over the last week, I've been having failures of Zigbee devices (mainly Lightify bulbs, but also Iris v1 motion sensors, ST motion sensors, etc.). Yesterday, all my bulbs failed to respond, motion sensors stopped responding, etc. Unable to factory reset and get them to pair (none of the bulbs), and all of the motion sensors. When attempting to pair, would only get "Devices Found", with nothing after that. Limbo-land.
After many frustrating attempts, and including restoring a backup from 10 days ago, still had same issues. Last ditch effort was to change the Zigbee channel being used. I know this is not recommended, or at least it may take hours for devices to come back on line. But, I changed my default Zigbee channel from 20 to 16, and VOILA!... I was able to pair all the devices (bulbs, sensors, etc.) successfully!
I am also seeing much faster response times with all devices and rules execution. At least for today, things seem much brighter!
Just thought I'd share and ask if there has been any discussion about changing the Zigbee channel or guidance on how to determine if there is interference with Wi-Fi?
There's been tons of discussions around it. Basically, depending on how you have your WiFi setup, you want your Zigbee channel as far away from your 2.4ghz WiFi channel as possible. The usual recommendation is to have 2.4gHz Wifi on channel 1 and Zigbee on channel 20.
However, I don't think that's your root issue. You mentioned Lightify bulbs. If you can replace them, do it. Most likely, they are the cause of your Zigbee mesh issues. Lightify bulbs are nasty repeaters that will destroy a good Zigbee mesh in a matter of hours or days. They are notorious for locking up (especially on a chatty mesh) and will take almost everything else down with them. If you can, replace them with something non-repeating like Sengleds and add some mains-powered repeaters.