My beloved HS103 (V5, 1.0.13) is acting up. It was stored with my chalet's Xmas light all winter, I've plugged it in and was working right away within the Kasa App Version 3.3.900 Build 1672. After a few minutes a pop-up suggesting a Firmware update was suggested, I've successfully did it and all was fine. Then, after a few minutes it started to turn my lights ON and OFF randomly.

I've pulled the HS103 and brought it home, on a bench with a light bulb, I've monitored it and can see it's going crazy. In the last 3 hours, it's been toggling between 2.5 min and 1.3 min ON and between 30 to 50 seconds OFF. Tried to contact support but they were no help.

No automation and not linked with third-party platforms. 

I do have several other HS103 both at the chalet and at home with no issues, but again I haven't done any other firmware updates :-)