I feel your pain 96 E300D!
My right rear regulator on my 300E just let go last night...I had replaced the left rear one last year!
Both had failed in the same manner...the track housing that holds the spring loaded cables in place wears out and allows the metal cover to loosen and freely move about while the mechanism operates. It starts off by getting in the way (i.e., window doesn't fully close) until the spring retaining clip falls off (kaboingggg) and the cable then gets tangled in the gear housing.
Fortunately the assembly w/motor isn't too terribly expensive (around $130 - $140), and it is a DIY fix. The hardest part of the job is getting that door panel off (after years of having the panel cure and form itself to the metal.
Yours might be different, but it would have saved me a lot of grief if I had known that the fasteners require lifting the panel vertically FIRST, then out! I'm used to yanking out VW door panels, I guess...
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car