problem could be cable, device or controls ?
cable - measure it from the zone used (controls, expander or keypad) check the terminations at device, zone & any joint box ect...
device - either wired up wrong, set up wrong, effected by the environment eg- this unit senses vibration of the back door slamming (or whatever ?) , or you might have a duff item
controls - the zone could be fcuk'd ?
That's the best my Psychic abilities can offer....