I and a lot of people that use motion sensors have or had this problem with false positives. I recommand that you loock to the following thread for a community solution created by @Mike_Maxwell. He has created code for an app which I use to have 2 or more motion sensors joined into a motion zone. If only one sensor becomes active, than this may be a false positive and the zone will not trigger. If all of the sensors are triggered in a certain time frame, than the zone is active and you can use that zone as a motion sensor for SHM in ST or Smart Alarm.