As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
MAGNETO ROTOR CRACKED AT THE SPLIT WHERE THE POINTS CAM GETS INSERTED. THE CRACK CAUSE THE SMALL ROTOR GEAR TO FALL AWAY AND LOSE CONTACT WITH THE DISTRIBUTOR GEAR STOPPING THE FUNCTION OF THE MAGNETO. BOTH SIDE OF THE SPLIT WERE CRACKED CLEAN OFF. MY GUESS AT WHY IT HAPPENED WOULD BE FROM SOMEONE LEAVING THE TIMING PIN IN THE MAG WHILE TURNING THE ENGINE IN IT PAST HISTORY CRACKING THE ROTOR.