I replaced mine. Unfortunately, the do not sell the motors separate for the rear windows (unlike the front windows). You have to buy the whole assembly which cost a little more than $100 new, unless you can find a used one. I tried to clean the assembly, oil, no go!. Have you try to close the door while holding the swicth down? If it goes down, your problem is most likely the motor. BIG difference with the new assembly, no problems since. If that is your problem, buy a new one and forget it for another 12 years.
Good luck!
J.H.
300E
P.S. Mine also had a "mild bow".