My 95 S420 needed (according to MB dealer) new mirror wiring harnesses on both sides. It was under starmark warr. still so they ordered the wire looms which tech says had insulation broken which was causing short circuits and keeping some of the movements from adjusting. Anyway, when they tried to do the work they realized they had ordered the wrong wires and the tech simply created the new wires and soldered in replacements of stock wire. Mind you I didn't really see any of this, because as you know they don't readily allow customer to watch-----but it now works correct and did'nt cost me so I stayed out of the way.
My fold function was also affected as was some of the movement directions. Its my guess that many of these cars have insulation breakdown, much as was widely reported on the engine harness. Perhaps folding movement (at cold temps) starts the trouble. I don't ever fold mine since I don't need to for parking and would never machine wash my car anyway. Some person my park in a tight city lot where they feel they have to fold, too bad. Also, if anyone tries to manually fold them they could be foulded up big time. Never allow manual fold. Luck fixing it. I do remember reading some posts about dissembly. Search , perhaps you will come onto those posts. A friendly, independent who would like to cultivate your future business might talk you thru the removal.
DanielW