If you occasionally get a random "Geofence Crossed" alert when the device (or your asset) hasn't moved it can be very worrying and frustrating.
GPS positions can vary sometimes, due to atmospheric conditions, interference, even sun spots .... That can sometimes create a small error in the GPS positioning - which can be up to 200 metres.
So if you are getting false alerts:
1. Check the centre of your Geofence is exactly where you need it to be (where your device should be)
2. Extend the geofence radius to at least 200 metres, preferably 350 metres
This will still make sure you get notified if the device moves out of the geofence, but will stop you getting messages when the device hasn't actually moved.