Not sure how old yours is or if this is the problem but some of the early ones did have a problem with the alarm going off when it should not. The problem was supposed to be due to the frequency used to set the alarm., They needed more different ones than were used which meant a Unicorn near to you might have an alarm on the same frequency and could set off your alarm when setting theirs. I think they could also disarm yours when doing theirs.
Not sure if there was a cure for this though, if that is your problem, but a Bailey dealer might know if no one else on here can help.