As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ENGINE HAD 200 RPM DROP ON LEFT MAGNETO. CHECKED MAG TO ENGINE TIMING, AND COULD NOT GET MAG TIMED TO ENGINE. REMOVED MAG FOR INSPECTION. WHEN MAG WAS OPENED, FOUND MAGNET SHAFT SHEARED AT KEYWAY. THIS MAGNETO WAS A NEW/REBUILD FROM TELEDYNE CONTINENTAL INSTALLED ON THIS AIRCRAFT 94.0 HOURS BEFORE.