Well, Replaced our old router anyway, and tried setting up all dimmer switches on the separate guest network a week ago. Also updated all dimmer switches to the new firmware version(1.04) when the...

Thank you Tony, Unfortunately, our router does not have a guest network setting. Also looking at Lightning16's response below, seems like that may not fix the problem even if I buy a new router....

I have 3 KASA dimmer switches (HS220 )installed in 2 rooms by an electrician. It seemed to work fine, no issues initally. When I have my LG smart TV ON in one of the rooms, though, I noticed the...