Device tracker groups.all_devices not working?!

Is it only me, who is experiencing some misbehaviour regarding the device tracker all_devices group?
I am using the Unifi tracker and it tracks device states. No problem at this point. But the group all_devices has the state ‘unknown’ and it does not change. I was expecting that the state is either home or not_home.
Is there something special that I have to be aware of since the unifi device tracker is an integration? In the past it worked all fine for me.