In my recent attempt to eliminate a squeal as my steps advanced out, I lubed the step bushings and then dis & reassembled the drive mechanism for greasing. Upon tryout, the steps advanced when the door closed and extended with it shut. I dis & reassembled several times thinking I had the gears out of time. No help. Since the electrics were working when I started, I didn't want to believe that they were an issue. They were not. I had disassembled the motor to check the armature bearings. Four bolts and the motor housing comes off exposing the brushes, armature and armature bearings. Turns out that I reassembled the motor housing 180 degrees from the original index.
D'oh! I was surprised that this alone will reverse the motor direction. Maybe the angular relationship between the permenant magnents and the brushes was changed or something. I was also surprised that the housing assembly wasn't fool proofed from bored factory workers and amature fixits like me.
If you go this deep, also be aware that the brushes need to be retracted before reinserting the armature or they will be damaged. On mine there were handy detents to withold the brushes. Just push the brushes back to the detents with a probe, insert the armature part way, then use the probe to push each brush forward off its detent. Then finish seating the armature.