Was the gear pinned? those un pinned factory gears sometimes slip when used with a HV pump .
imo the bearings lost oil pressure, and might wanna check the journals for tapper.
.002 should have lived
When starting out as a kid...i assumed the shop cleaned out the galleys for me, i was wrong...all mains were washed out , lil/big copper grooves all over them, still rev'd 7k and never let loose though.
I dont believe 'unless u can show some down to the copper bearing' that u had a bunch of crap go through them.