I once took apart the driver's side console window switch on a 77 300D. They can be disassembled and cleaned. I used a pencil eraser and a paper towel sprayed with WD40. You could also use a Scotchbrite pad.

There are a lot of little parts (springs, pins, and the like), so I did mine at the kitchen table with lots of good light. The pushbutton to lock out the rear window switches can cause your problem, so I'd clean this one too.

It's amazing those switches work as long as they do, considering how much dust, lint, and miscellaneous spills get in there. You can just get new ones, but cleaning them just might be enough. If you take one apart, you can see why they cost about $60.