As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THERE WAS A ROUGH MAGNETO DROP DURING RUN-UP. TROUBLESHOOTING REVEALED A LARGE MAXIMUM POINT GAP AND CORRESPONDING ERRONEOUS E-GAP. CLOSER EXAMINATION REVEALED THE TUNGSTEN CONTACT BECAME UNATTACHED FROM THE RIVET ON THE FRAME SIDE OF THE CONTACT ASSEMBLY. THE REMAINS OF THE TUNGSTEN CONTACT WERE FOUND INSIDE THE HOUSING OR FELL OUT WHEN THE MAGNETO WAS DISASSEMBLED.