Entrance steps won't go out

My memory is a little foggy about exactly what I did to make it work. I may have had to remove the snapring to swap the gears but I'm not certain. It worked great. If the steps go the wrong way, just reverse the wires to fix it. I replaced the motor on a friend's steps. A few months later he showed up to an outing with our group and said they stopped working again. When I took the motor off and opened it up, I found the remains of the 3 plastic disks that should work as shock absorbers had turned to powder. I cleaned them out and reused the ones from the original motor. They were still working when he sold it. Never did figure out what happened that made them pulverize like they did.