Rebooted WiFi extender and have not had any problems with it since. The two new smart plugs (HS100 v2.1 firmware 1.5.8) are now dropping off (going red) the network every few days. I have moved then...

I have 9 smart plugs. 6 are on the main home WiFi network and 3 are connected via a WiFi extender (in the garage). Normally I can see and operate all 9 via Kasa on my iPhone when it is connected to...