I have the exact same issue as described in this previous post:
https://community.tp-link.com/en/smart-home/forum/topic/641150

I'm disappointed to see that there was no answer resolving the issue from 2 years ago.

I currently have several KS220M installed in three bathrooms in my house. Everything works for a while, but then they just stops working (never all at the same time. When this happens, it's like the affected dimmer's hardware has crashed. Even the physical buttons do nothing, Nothing works. ie. If I attempt to trigger it using the motion sensor, the physical button, or the app and the light doesn't change states (sometimes it is stuck off, other times it is stuck on). It continues to look online in the app.

When I press the restart button on the right, bellow the main switch, the switch reboots and works again for a while.

This is happening often enough that I may have to remove them.  🙁

Has anyone else had this same issue and found a fix?