Quoted from ArcadeDanger:however, motor stays running, and the decrement coil on the replay unit keeps clicking away (it's at 0 as recommended by pinrepair.com).
Check the Replay stepper switches. And do you have a high-quality schematic scan? The one on IPDB is a disaster.
Check out Clay's guide on stepper units: http://www.pinrepair.com/em/index2.htm#steps