Would a broken door mechanism set my alarm off randomly?

My car alarm keeps going off when theres nothing or no one near it, its a toad ai606 on a fiat punto, been in there for a long while now and its never done it before, ive had the sensor turned right down to hardly anything and it still does it? does anyone have any ideas to wether the mechanism would cause it? when it goes off and i turn it off it beeps 5 times which is something is stil open.... which it isnt :S