As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING A 500 HOUR INSPECTION OF MAGNETOS, IMPULSE COUPLING WAS FOUND TO HAVE CRACKS IN THE HUB BASE PLATE, LOCATED AT THE FULL ADVANCE STOP NOTCH. CRACKS RADIATE FROM THE SHARP-CORNERED FEATURE OF THE NOTCH OF THE PLATE. DEFECT DETECTED USING MAGNETIC PARTICLE NDT TESTING. WE HAVE SEEN THIS SAME DEFECT ON A LARGE PERCENTAGE OF SLICK MAGS USED ON THE 6 CYLINDER ENGINES.