As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SB-643, C/W, MAGNETO INSTALLED IN ACFT. ACFT FLEW 5.0 HOURS AT WHICH TIME, PILOT REPORTED A DEAD - CUT WHEN SELECTING THE LT MAGNETO ON THE RUN UP ON THE FIRST FLIGHT OF THE DAY. MAGNETO REMOVED AND FOUND THAT 1X TUNGSTEN DISCS HAD SEPARATED FROM MAIN CONTACT POINTS AND ENDED UP SITTING IN THE CONTACT POINTS COMPARTMENT CAUSING AN EXTREME CHANGE IN MAGNETO TO ENGINE TIMING. MFG NOTIFIED.