As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) ON LANDING, ENGINE BECAME NOTICEABLY ROUGH. AFTER LANDING A MAGNETO CHECK WAS ACCOMPLISHED. THE MAG CHECK REVEALED THAT THE RT MAGNETO WAS NOT FIRING. UPON INSPECTION OF SAME IT WAS DISCOVERED THAT THE INTERNAL NYLON GEAR HAD FAILED (TEETH STRIPPED). MAGNETO WAS REMOVED AND A NEWLY OVERHAULED MAGNETO WAS INSTALLED.