As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT REPORTED THAT WHEN REDUCING POWER WHILE TRANSITIONING FROM CLIMB TO CRUISE, THE LT ENGINE PROPELLER RPM STAYED AT FULL RPM AND WOULD NOT REDUCE. THE PILOT ELECTED TO RETURN TO THE DEPARTURE AIRPORT. AFTER MX INSPECTION, THE DISCREPANCY WAS UNABLE TO BE DUPLICATED. AS A PRECAUTION, THE PROP GOVERNOR WAS R & R AND THE ACFT WAS RETURNED TO SERVICE.