As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) ENGINE STARTING RUNNING ROUGH IN CRUISE FLIGHT PILOT RETURNED TO STATION. GROUND RUN INDICATED EXCESSIVE RPM LOSS ON RT MAGNETO. MAGNETO REPLACED AND FOLLOW UP GROUND RUN CARRIED OUT RESULTING IN NORMAL RPM (STATIC) AND RT RPM DROP WITHIN LIMITS. NO APPARENT EXTERNAL PROBLEMS WITH MAGNETO COULD BE IDENTIFIED. AN SC REPORT MAY FOLLOW SHOULD WE CHOOSE TO HAVE THE MAGNETO OVERHAULED.