I have had 3 switches fail after a 100K each time. The main switch console for all the power windows was made in Mexico, at the price Mercedes would normally pay for just one switch, so you get what you paid for, even the Mercedes mechanics know the switch console is a piece of junk. I have 3 solutions not including changing cars, leaving the window down or up, but in a MacGyver way of remedying the issue for ever.
1. I've broken the switch cap and leaving part of the knob, I attached a small pair of vice grips which although looked awkward did the job of providing additional movement for the switch to make contact where over time the contacts have burnished, or covered with electrode dust that you can't get to to clean.
2. I've whittled on a ink pen casing to match a snug fit over the knob, and it still provides leverage to use, although I seem to loose the lever between the seats.
3. The best way to eliminate the issue and make the car still resemble the luxury we thought we were getting is to by-pass the switch and install a 3 way toggle you can get down at the parts store. If you wish to install as many toggles as there are in the console, just let the module be lowered into the well below the place it fits and install the toggle switches through the same holes in the paneling and use some nice washers to seal them up tight. Now just do some simple wiring into the switch console and attached with cover plates. My SUV is going on 450K, and with each new adjustment it improves in value, even though it may not be pure Mercedes, they knew it when they built it to a price point rather than building the car and figuring out the price. I - hawserman