As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) PILOT REPORTED ENGINE RPM INDICATING HIGH AND ROTOR RPM INDICATING LOW. GOVERNOR HUNTING DURING GROUND RUN. A HIGH PITCH ABNORMAL NOISE WAS HEARD WHEN REDUCING POWER SETTING. MAINTENANCE OBSERVED ERRATIC TACH INDICATION DURING GROUND RUN. RT MAGNETO REPLACED.