I have a motion detector that behaves very odly.

In wet conditions, ie: rain and wet ground/landscape, it works as expected, ie: switches on with motion sensor, stays for the time set, switches off and stays off until motion is detected.

In dry conditions, it switches on, stays for the time set, switches off and then on again within a couple of seconds, and repeats forever.

I swapped with another one around the house, which is working perfectly, same behavior when fitted to this position.
I swapped a new one, same behavior.

I tried to change the position of the sensor, sensitivity etc but no luck.

This was working fine until the house was painted with semi-gloss paint. Coincident? but why if it is the cause? and why only in the dry?