Have you actually checked the crank runout? Have you checked the bearing alignment inside the case? Have you checked the fit of the bearings in the case? You will need to use some good machine tools to do this. Two of the three noted above have the ability to stop an engine in it's tracks and shatter the prop in the process, although I tend to think the prop bolts may not have been torqued correctly to begin with.

There is a general assumption that our engines are manufactured with a high level of precision while using excellent QA methods. If only that was true....

Look at everything before making the conclusion.