Flood light

Have 3 flood light cameras, sometimes at night I notice that the lights are on but there was no event recorded. They are connected to 5 chimes but none sounded. The lights will switch off after a minute or so but come back on after a little while. I've set people only, reduced motion settings (zones, sentitvity, people mode) but nothing has any effect. Sometimes there is wind moving tree branches near the lights but that doesn't explain why no event is recorded, just the lights being on. Ideas and suggestions welcome.