I have a 2016 GLE 350 and when I slow to below about 15 mph I hear a switch engaging and then disengages again above 15 or so mph. The sound comes from the rear Liftgate area. It is the same sound the camera makes when you are stopped and put the vehicle in reverse. It sounds like that every time I slow below a certain speed and then go back above. Taking it in for service but am afraid I will get the standard, "they all do that" response. Anyone familiar?