My cupholder had a lot of spillage in it from a previous owner. The dor worked OK so I just took apart the up/down cupholder ass'y and washed it (after soaking in hot H2O and dish soap) it cured it - now works like a charm. I did not lubricate it but if you want to try that first I think a dry silicone lube would be better than a petroleum based lube. I also drilled a small hole in the very bottom of the cupholder in the center and put in a short self tapping trim screw to stabilize it in its opening (I don't remember if it was broken or just worn but it was loose and the stability keeps it from binding).
My dash openings work fine, you might inspect them carefully from a close angle with a bright light, I found the previous owner's eyeglass prescription wadded up behind the ashtray door which casued a crinkling noise each time it opened.
I also had to clean and lube the bellows on the glovebox door there are some instructions
I have a friend from church who owns a MB and that's HIS name; pretty small chance huh. RE the relatively small crises dealt with here; this forum is EXACTLY for these tiny minutiae that PLAGUE the world of the super-rich (AKA Mercedes-Benz owners)
Thank GOD we can concern ourselves with these problems and not any "real" problems.