As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT REPORTED FAILED RT MAGNETO. REMOVED MAGNETO FROM ENGINE AND DISASSEMBLED. FOUND ONE OF THE COIL ANCHOR WEDGES WAS DISPLACED AND HAD MIGRATED ONTO THE SECONDARY TOWER. THE TOWER WAS BURNED AND MELTED AND THERE WAS OBVIOUS SIGNS OF A DIRECT SHORT AT THE SECONDARY TERMINAL CONTACT TAB.