As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT REPORTED MAGNETO ROUGH IN FLIGHT. MAINTENANCE INSPECTED AND FOUND OIL IN THE #5 CYLINDER. UPON REMOVAL OF THE CYLINDER IT WAS FOUND TO HAVE MISSING MATERIAL AT THE VALVE INTAKE GUIDE. THE #5 CYLINDER WAS REPLACED WITH NO FURTHER DEFECTS NOTED