Long story short, you had earth cable fault somewhere and the indicator light is just false positive due having short from neutral/live to earth from an appliance that only turned on during day or night.

This post has been edited by jio: Oct 21 2023, 12:25 PM

Did you test using the same socket/circuit as the device with the indicator when the light is off? Can the socket tester trip the RCCB? If yes then it's the device with the indicator itself having problem.