I checked it again. On the manual start it moves, not sure all the way, but does not retract fast enough before the unit runs to fast. It does seem like there is a lot of resistence moving the arm back and forth
Can you determine if the resistance is in the motor or from the linkage and throttle plate? If it's in the linkage and throttle, look for something binding. If it's in the stepper motor, replace the motor.