Slide not working (motor runs but slide doesn't move)

He needs to start taking things apart until he finds the problem. I would suspect the gear box on the motor or one of the drive gears. Yea, they all have pins holding them on the different shafts. It aint rocket science. You have a motor, a gear reduction box of some sort, a gear and a gear rack. Broken tooth on a gear, or a broken gear box or pin is about all it can be.