The only time I see the SPC/Signet wireless devices go discon is either when the tamper is open or the battery is removed. Apart from that I'd say faulty sensor
Just a heads up that the the latest firmware 3.3.5 blocks a lot of dial capture units.
If the HKC panel sees anything under 30v or so you will get a line fault error. MiniAir units and their clones seem to be impacted