The reverse lights on my 1979 300D are playing games. When I shift (auto) into reverse they will only sometimes go on. If I jiggle the shifter they will usually come on, but often go right back off again.
During heavy rains, with the car left outside, I notice water on the rear passenger floorboard. Sometimes enough where it has actually soaked through the carpet and sloshes around when I drive. There are no visable leaks in the interior, not through the sunroof, doors, windows, nothing indicates a water leak. The water just seems to appear on the floor after a good rain.