I have had a dozen Sonoff devices running for over a year - with little or no problem.
I have a stable Meraki WLAN (2 x APs) providing excellent 2.4Ghz coverage everywhere in the house.
I have a range of models - T1UK3C, T12C, Basic, S26 and S20 - all on latest Firmware.
Starting the week of 18th November all the devices are falling off the Wifi. I believe they are not talking ( sending hellos ) and therefore are being disconnected from the WLAN. the WLAN logs show: "client association expired" for all the SONOFF devices.
My S20 plug will not power up often - it does not even flash green once after I plug it in and then when I leave it unplugged for a time - it does reconnect, with a solid LED but seems to drop if if try to send a on/off from app.
Finally I have a basic that no longer has ANY led in use - despite the device seemingly working fine. I have not hidden the network stats LED.
I have tried many things on WLAN - clearing ARP, Binding IPs, but SONOFF devices (only ) are still affected.
Should reiterate I had over a year of almost flawless operation up to last month.
Have you any advice.,