Had this problem with my garage door opening at random times. Figured it was the external fixed code receiver, so I replaced everything with rolling code receivers, with matching transmitters obviously. So big was my surprise when a friend visited and my garage door opened as he was locking his car. Turns out I forgot about the integrated receiver on the garage opener. And this turned out to be a fixed code one as well. Had no luck in getting any information from the company who installed the garage opener about disabling the receiver, and google led me to other people who had the same experience. So firstly I cut the aerial off the built-in, which limited the range of the old transmitter, but it was still triggering if I got closer to the unit. Turns out the solution was even simpler. Just put the integrated receiver into learning mode with a simple jumper (connect middle and B as per the image) and no remote will ever trigger it again. Problem solved.