Does the window move smoothly and easily in the track? If not that's probably what's taking out that motor.
I think you are wise to keep looking for the cause of the breakage.. maybe there is enough internal friction on all the rubbing parts put together to wear out the gear quickly.?
On one of the 1/4 windows on our power-window '65 Satellite (when Ma Mopar raided an Imperial power motor and gearbox for the 1/4 windows
for a one-year-only transition), the window sliders and guides operate smoothly, but the reproduction window whiskers were just too thick and created a lot of drag on the glass.
I foolishly let the power of the motor just overcome the drag, but it didn't take long for the gear box to break.
Lesson learned.
- Art