Sounds like the ball count stepper is out of whack slightly... largish disc with brass buttons that has an arm that moves over it.
You can move the arm manually while machine is on by pushing the coil plunger in.. this will increment it one step.
Start on ball 1 and manually move the arm... look to see if ball 2 is now lit etc.
If not, the problem should be evident by looking at what's touching at the disc and wiper