As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING PERFORMANCE OF FIRST 500 HR INSPECTION OF MAGNETO, CRACKS WERE DISCOVERED IN IMULSE COUPLING SHELL. CRACKS DETECTED BY NDT/MAGNETIC PARTICLE INSPECTION OF PARTS. CRACKS RADIATE FROM SHARP CORNERED FEATURE OF SHELL THAT FORMS TRIP DOGS. SUSPECT STRESS RISERS CREATED AT SHARP COMERS RESULTED IN CRACKS. ALL 4 MAGNETOS FROM THIS ACFT HAD SAME DEFECT PRESENT, REQUIRING REPLACEMENT OF IMPULSE COUPLING ASSEMBLY.