I have these issues as well for the past 1.5 years. After setup everything works great but after a few days the system fails to see motion trigger events and the alarm never goes off. Right now none of my sensors will trigger the alarm. Before, only my house sensors would work but would delay the alarm as much as 30 minutes. Sitting down watching TV and then the alarm goes off and I'm stuck on the ceiling.
Using the heal node button in the v1+ release seems to fix this problem but I have to do it with each sensor and to do this I have to remove the sensor from the wall and press the pair button for it to work.