The passenger side rear window on my 300SD stops about 4-5mm short of going all the way up. When it reaches that level the motor keeps going, but the window just lurches up and down ever so slightly. I can pull it the rest of the way up and it will stay there.

When I try to roll it down from its 4-5mm peak, it won't go down unless it's a hot day, in which case it will usually work. If I have pulled it all the way up, it won't go down at all.

It seems like a gear issue. I have had the door panel off and I don't see any adjustments other than the stop for when it's all the way down.

Where should I go from here?