trigger Signal Policy and Inactivity Timer

For testin purposes i've made 2 kind of settings for our mobile terminals Device inactivity, this triggers a script wich kills some applications after a certain time (approx 1,5 hour). I'm aware this is only working when the devices are not attached to a power source. The second settings is a signal policy, to cover this when attached to a powersource (event is-charging) to trigger the same script after the same time.   I'm noticing that (mainly) the Device Inactivity triggers random during the day. Sometimes 2 or 3 times within an half an hour. Sometimes the Signal policy won't start