Look at my threads on 300CD door seals. I have a few. It appears that currently, Photobucket removed their ransom fee so you can actually see the photos too!
Here is the final one. I did finally solve it. I was at my wits end.
Read this thread all the way through:
http://www.peachparts.com/shopforum/diesel-discussion/314303-w123-coupe-window-adjustment.html
Your situation sounds like mine!! Adjust and adjust, per the FSM, and no dice. Why? Because one of the stops was actually upside down, apparently from the factory.
I would adjust and adjust and think that things were about right, and then fail.
Looking up in the door and observing the direction of the stops made it all click.
Alas, I still haven't buttoned that car all back together...
Let me know if you have questions. Since my car is still open I can go into the garage and have a look to help answer questions.
Good luck!!