I would attach a micrometer to the base housing so that its tip just sits against the worm attached to the motor and run the motor. If the worm is oscillating it will show on the dial with the needle oscillating with movement of the worm. I would bet that is where the problem is. As indicated previously, I would contact the person who did the motor replacement. The Byers worm sets are excellent and far superior to anything Meade or Celestron ever put out. The problem started after the motor replacement which indicates strongly the problem is either with the motor or the shaft from the motor.