Hue Motion Sensors dropping out

Hi,

I have set up two seperate zones both with 2 Hue motion sensors. They are triggered when motion is detected and the lux is less than a value. It works fine but then will stop working sometimes starts again on its own and sometimes i have to repair one sensors and all works fine again. I added a restart Hue Bridge at 4 am ever morning but still having the issue. Any ideas what could be the issue would be appricatied.

Thanks Andy