As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW EXPERIENCED NR 1 ENGINE FLUCTUATIONS DURING CLIMB. NECESSARY CLIMB POWER SETTINGS DID NOT AFFECT THE INDICATIONS. AIRCREW DECIDED TO RETURN TO BLOCK IN ORDER TO BE SAFE AND HAVE MAINTENANCE LOOK INTO THE ISSUE. MAINTENANCE LOOKED INTO ISSUE, CHANGED OVERSPEED GOVERNOR AND PROP GOVERNOR. NO FURTHER OCCURRENCES.