Honeywell Wifi Thermostats Periodically Lose Wifi Connection - Restores with modem/gateway restart
I have 4 Honeywell Total Connect Comfort Wifi Thermostats model RTH9580WF1005. I have had them for 5 years and until recently, they generally stayed connect to Wifi. My gateway/modem/router is a BGW320-505, software version 2.14.4. Every now and then (maybe 3 or 4 times a month) at least one, sometimes more, of the thermostats will lose their wifi connection. Most of the time, if a wait for a day, they will reconnect. If that doesn't happen, if I reboot the network (using the ATT Smarthome App / Network / Restart Wi-Fi Network (when seems to restart everything including Uverse and ethernet connected connections), 100% of the time the thermostats reconnect to the network.
I get emails from Honeywell Home whenever they connect or disconnect. It seems like they generally lose their connection around 1 AM (+/- 30 min) or 1 pm (same). And when the reconnect on their own, it generally happens in those same timeframes. So my suspicion is that the modem is doing some routine cleanup/testing of its connections at those times and for whatever reason, it is unhappy with the thermostats and drops them.
I see this same phenomenon less frequently with other smart home devices, especially my MyQ hub for my garage door openers. It used to happen with my Rachio sprinkler, but that connection seems pretty stable now. I also see it occasionally, around the same timeframes, with some switches and plugs that have been flashed with Tasmota. But it happens most often with the thermostats.