Back up camera screen is black with the sidelines when in reverse

The common failure item for these is the wiring that comes from the body up to the trunk lid. It has a bad habit of breaking and causing the camera to fail. There is a service bulletin LI54.65-P-047195 on this issue and the repair uses a newer cable. Testing for the break is simple. Use your fingers and pull an area of the cable like you are trying to pull it apart. Watch the insulation between your fingers, a break will usually show up in a spot by the insulation forming an hourglass shape. You may also feel the break as a hollow area if you squeeze the insulation of the cable. Replacing the cable isn't difficult and doesn't require that the camera be calibrated. The cable follows the harness from the camera down to the control module.
Replacing the camera unit or the power module however does require specific calibration. As for checking the signal, the wiring from the camera to the control module only has a video signal, the module translates that and sends it to the front on the CAN line. Mercedes doesn't show the functions of the various wires in any service information except in the online dealership system.

Great to hear. Wish they were all that easy.