I agree with Dadeaux... Take a soft hammer (or even a hard one) and crawl under, KEEP CLEAR OF THE STEPS, Tap, firmly (do not shatter) the motor then have your partner open the door KEEP CLEAR OF THE STEPS.. I've had to do this 2 or 3 times.
I finally re-indexed the motor... What, you ask, is indexing?
The motor stops at exactly the same spot every time you close the door (Also the same, but likely different, spot when you open) and sometimes this is exactly the WRONG spot for the motor.. I opened the transmission, and re-positioned a gear, then re-assembled.. NOTE: there are small parts that tend to fall out when you open so be very careful (just a washer or gear)
I have not had a problem since.. OF course I keep things crossed
Home is where I park it!