@laoadam Your garage door safety sensors may not be aligned quite right. It could be off just enough that vibration from the door itself when opening and closing is knocking one of the sensor modules out of alignment. The same could be true if one of the wires to it is loose. Check both sensor modules to make sure they are aligned right and not loose. One should be a transmitter that shoots a beam to the other module which is the receiver. If the transmitter beam is not aligned exactly right with the receiver, it won't work. As I mentioned too, check that there are no loose or broken wires. If wires go to screw terminals, make sure those are secured properly and that none of the wire casing is getting pinched in with the wire as that may cause a partial connection that could be lost with vibration of the door. With all that being said, this is a forum for a DIY home automation hardware platform called MySensors. Were you planning at some point to implement this for your garage door?