I have been testing a set of four valves in one room since March 2025. They taked the temperature from T315. I created a group. Everything worked as it should.
However, I needed to change the user in the app (for personal reasons). The only way to do this was to restart all devices and reconnect them to the app.

To my surprise, before the restart, all valves showed a battery status of 3/4.

After restarting (after 5 minutes) and connecting to the app, the battery status changed dramatically. Some are dead, some are almost dead. I even put in new batteries, but the result was the same. Only the 4th valve shows 4/4, probably because I had to remove it during installation...

Kasa App 3.4.402
Kasa KE100 1.0  Firmware 2.10.0