Had the same kind of problem with my coach. Found it was in the connection between the cable than ran the length of the coach and the one that goes to the camera. It's a bad design allowing the connection to fail inside the connector. Could not locate a replacement connector so I just solder spliced the wires together, removing the connector all together. Only took a few minutes and have not had a problem since. If I ever replace the camera I will either try to get a connector or just hard wire it in as well.
To find the connector you must remove the camera, the extra cable is just hanging there.