I have a Sear's Garage door. Whenever I press the remote control or wall opener, the door goes about 5 inches down, then comes back up as if something is in the way and causing the door to go back up. The lights are clear on both sides and I cannot find any spiderwebs or anything that is making this happen. Does it appear I need a new unit? Could there be a short in it? The power to it is working fine (I would guess since it does attempt to work). HELP!