Here is a nice article I came across talking about bearing wear/spun bearings:
http://www.enginebuildermag.com/2017...spun-bearings/
The author mentions engine lugging as a possible cause, and I had mentioned that earlier. I'm thinking on the babied S54's with bearing wear, lugging and cold/dry start are the likely culprits, but it would be interesting if some combination of events is causing low oil pressure. Maybe we all need to install oil pressure gauges.
Salty