Is it attempting to advance (solenoid firing for the step-up portion of the Ball Count Unit), and simply not turning? Or is the Ball Count Unit remaining inert when the ball drains and just kicking out the ball again?
When you manually advance (and reset) the Ball Count unit, does it seem sluggish at all, or really smooth? I'd advise cleaning all your steppers no matter what, but check that one out first. Any other systems/issues, or is everything else working well so far?