My driver door barely ever locks or unlocks. I have an aftermarket alarm and when i hit unlock, all the doors unlock but i hear a buzzing in the drivers door. Sometimes the lock moves a little bit. Usually when i lock my car, i have to lock the drivers door with a key. The buttons on the two front doors don't work either. Usually if i hit the lock/unlock button the lock will work once, but after that it will only buzz and vibrate. The guy who installed my alarm told me he thinks it could be the door lock actuator and suggestedi get another one from Ford a.k.a "those Ford ********" (we've been through this before). I don't think cleaning the contacts is a remedy for this.