As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING A 500 HR INSPECTION, IT WAS DISCOVERED THAT THE OIL SEAL WASHER IN A MAGNETO HAD MOVED OUT ON THE SHAFT AND WAS HOLDING THE IMPULSE COUPLING PAWLS IN RUNNING POSITION, CAUSING ADVANCED TIMING FOR START. AT 15 HRS AFTER 500 HR INSPECTION, CONDITION OCCURRED AGAIN. MAGNETO REPAIR SHOP SAYS THIS IS THE 8TH OCCURRENCE OF THIS CONDITION THEY HAVE SEEN IN THE LAST 12 MONTHS.