The early rear window regulators on W201's went through at least two redesigns. We had to have ours replaced (under warranty) twice. Eventually the problem was fixed and we had no further trouble until we sold our 18 year old 190D.

The only window problem I've had with my '91 300E is that the switches need to be worked occasionally.

I believe that Mercedes began to fall off after 1992 when the company was no longer controlled by engineers. Up until that time, the engineers designed the car BEFORE it was priced.