All, I wanted to follow up on my original post. It ended up being a small (1/4) inch Allen plug maybe used during engine manufacture. It is near the oil pressure switch and evidentially never tightened. It was barely in and getting ready to blow out completely (maybe next time the engine ran). All I had to do is tighten it with an Allen wrench and it’s fine now. But I never considered it as a possible source because it’s so small and is just a (dummy) plug. I feel lucky I found it before total blowout and all is good now. I get the impression that pandemic assembly processes might have been a bit sketchy!
