As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FAA-PMA PART AM-3215 CARBON BRUSH AND SPRING WAS FOUND BROKEN OFF FLUSH WITH THE SPRING AND FELL INTO THE MAGNETO. CONTACT WAS MAINTAINED BY THE REMAINING PART OF THE BROKEN BRUSH. DURING THE PREINSPECTION RUN UP, THERE WERE NO INDICATIONS OF A PROBLEM. THE BROKEN OFF PARTS OF THE CARBON BRUSH WAS LOCATED DOWN BY THE COIL AND WAS DISLOGED BY TILTING THE MAGNETO UPSIDE DOWN AND SHAKING THE MAGNETO.