As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
'ACCESSORY CASE OIL LEAK'. A FACTORY LYCOMING ENGINE HAD A PERSISTENT SLIGHT OIL SEEP AT THE MAGNETO BASE. AFTER REMOVAL, IT WAS FOUND TO HAVE A FLAW IN THE APPARENT CASTING. A LOW SPOT IN THE GASKET AREA ALLOWED OIL TO SEEP BY. PART WAS REPLACED FOR THIS REASON AS WELL AS FLANGE/CLAMP WEAR.