Timing chain confusion.

[Accelo]

If the tab is correct, then the outer ring on the balancer has moved in relation to the keyway in the snout of the balancer.

This could indeed be an issue. Another thing that will cause the same issue:

Don't forget, there are two key locations on the balancers. Early timing marks are aligned with the keyway. Later are off as they relocated the timing marks. I am unsure what year this changed. If the balancer is not original to the motor and matches the location of the timing tab you will have issues.