Peteforsure

When putting my 2008 CL550 (w/ 40k on the odo) into reverse I get a left rear back up light malfunction indicated on the dash and of course, it's correct, the left rear light is out. In conjunction with this the rear camera screen goes black after about 10 seconds... it works at first, but then goes black, leaving just red driving lines to follow... but nothing to guide against as the screen is black. I replaced the left rear module as replacing just an errant bulb is not the alternative. But that didn't change anything and, on wiring a 9v battery to the original back up light, it worked fine. Soooooooooo... there's a gremlin somewhere. The dealer said it was a new one for him (I get that a lot) and they'd have to spend time tracing the fault. I can see this morphing into the price of a new car. Any thoughts or experience w/ this one? Many thanks! Peter (ps. I have an Audi, a BMW cycle etc., and all of these sites seem to be designed by the same fellow... and w/ all due respect, apparently there's a learning curve I've yet to master so, whoever has the answer to my riddle feel free to email me directly w/ either the answer or to advise that one's been posted here...peterbbell@gmail.com)