2015 ACE 29.3 has Velvac mirrors, may be the same for yours. The wires on mine:
From display in dash to camera selector switch in dash accessible through the removable panel above steering wheel. RCA to RCA.
Each camera is attached to the selector switch via cable with a Voyager 4 pin connector.
There is probably another connection point at the mirror to allow mirror removal as BobGed said. I haven't taken that connection apart yet.
If you have a loose connection, it is probably not in the cable from the switch to the in dash screen as you would have the issue with all cameras. May be in the cables from the switch to the camera.
Have not figured out how to remove the mirror yet. Mine is a little loose, would like to tighten it up some.