As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) CSU (PROPELLER GOVERNOR) ALLOWING PROPELLER RPM TO CHANGE WITH TORQUE CHANGES, AS POWER WAS ADVANCED OR RETARDED THE PROP RPM WOULD RISE OR FALL BY UP TO 75 RPM PRIOR TO THE GOVERNOR CATCHING IT AND GOVERNING RPM. CSU WAS REPLACED WITH A SERVICEABLE UNIT. NO FURTHER DEFECTS.