[CSX 4027]

I would not hazard a guess as to what might actually be the issue here until a thorough examination of the build was disected. I mean tear down. Only then will you know the true answer. I have seen the best engine builders make mistakes. It happens but, I am not saying that is the case. You need to look beyond the Monday morning type quarterbacks.
Isn't that why we have MRI's for people?