The FIBARO Motion Sensor indicates a light intensity which seems wrong to me.
1. The battery is almost discharged.
Replace the battery by opening the housing cover. Then close the case and put it back in place.
2. The FIBARO Motion Sensor is placed too close to a light source.
The FIBARO Motion Sensor must be placed in a place where you want to detect movements and where you can read a reference brightness. Avoid locations exposed to a direct light source.