Motion sensor alarm issue notification good?

My motion sensor is set up to give me notifications even when the system is not armed. This works fine I get the notifications when there is motion. Problem is that after I arm the system I will get false alarms from that motion sensor, seems to as quickly as ever 5 minutes, I will turn system off, get no notifications for the motion but when arming system again after a while still false alarm from motion detector. Anybody have any idea what's going on?