
EDIT: don't know if it was coincidental or not but at the time of the disconnect there were no devices connected to the 2.4ghz band of the router. After a reboot some devices switched back from 5ghz to 2.4ghz and the thermostat is also connected again. This makes it hard to debug as both 2.4 and 5 ghz use the same SSID and all but 2 devices can connect to both bands. The thermostat and my smart scale are the only 2 that can't. The scale only connects once every 15 hours, so I can't say definitively if the router didn't emit over 2.4ghz and it was impossible for the thermostat to connect or the bug triggered again.