As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING FLIGHT, THE NR 1 ENGINE OIL PRESSURE DECREASED TO 52 PSI, ALONG WITH SOUND OF RELAYS CLICKING IN PILOTS SIDE PANEL. WHILE THE PROPELLER WAS IN FEATHER OIL PRESSURE RETURNED TO 60 PSI. REMOVED AND REPLACED THE P2.5 SWITCHING VALVE.