Estod, it aint unheard for oil pump screen to git trashed with grit. Also seen screens punctured with nut's bolts and whatnot in the sump gettin sucked into oil pumps gears Pulling the sump aint bad idea, specially if its high mileage engine. Then just cleaning the crap will make it worthwhile chore.

Otherwise worst case scenario nobody's mentioned yet - spun rod bearing For this i been told one diagnostic method is check the oil filter for metal shavings using magnetic probe. Heck use the same metal shavings search method prowling the sump to help eliminate this worst case scenario.