As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT REPORTED RT MAGNETO TO BE INOPERATIVE DURING GROUND RUNUP. THE ASSIGNED TECHNICAN REMOVED THE RIGHT MAGNETO AND FOUND THE CAM SLOT ON THE ROTOR SHAFT COMPLETELY SHEARED OFF. CAUSE UNKNOWN POSSIBLE PART DEFECT. THIS MAGNETO WAS INSPECTED EVERY 500 HOURS.