As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AT CRUISE FLIGHT NR 1 PROP EXPERIENCED RPM FLUCTUATIONS. AS A PRECAUTIONARY MEASURE, PROP WAS FEATHERED. PILOT LANDED UNEVENTFULLY. FOUND REGULATOR TO PROP, OIL TRANSFER TUBE, O-RING CUT. INSTALLED NEW O-RING. GROUND RUN FUNCTIONAL AND LEAK CHECKS GOOD.