I've never had a window gearbox go bad, but I've heard it does happen quite a bit. I have had a number of the plastic window knobs strip out (plastic gets brittle and splits open). Before you replace expensive and more difficult to change window parts, try swapping out the knob with another one that seems good and see if that helps!
2007 T-286SR Cherry/Granola, #6236, original owner, current mileage: 9467.8 (as of 5/26/19)
1997 T-2653 Blue Denim, #5471
1979 12 1/2' MC, Beige & Avocado, #4639
Past Sunlines: '97 T-2653 #5089, '94 T-2251, '86 T-1550, '94 T-2363, '98 T-270SR