As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT REPORTED ENGINE RUNNING ROUGH. PERFORMED TROUBLESHOOTING, FOUND RT MAGNETO ROTOR SHAFT AND ROTOR GEAR WORN BEYOND LIMITS. GEAR WAS FOUND LOOSE ON SHAFT. THIS IS THE SECOND SUCH 4300 SERIES TYPE MAGNETO WITH APPROXIMATELY 500 HOURS TT WITH THE SAME PROBLEM.