I don't know the history of your engine, the machine work performed, or the skill implementing it all. What I will say is we have a small shop and accepted a grenaded(!) GM 6.2 engine job. My cohort is doing the work. After full assembly, it knocked violently shortly after the initial start. Apparently, shrapnel from the original piston exploding issue lodged itself where it wasn't easy to clean, in the intake manifold. It got built a 2nd time. (Not started yet...)
Point I'm trying to make is that small bits of debris from previous disasters may be haunting you now. Something to think about.