El.,

You are still talking about a manufacturing control problem or perhaps
worn CS gear problem. Both are solved by either returning the prop back
or replacing parts. I had similar issue with my IVO magnum prop (200hp
franklin) in which case an exchange of blades improved the situation.
Generally once you take care of that problem it does not return. But
dynamic imbalance can be a recuring problem - simple nicks or blade
wear will do it.