As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT REPORTED REAR ENGINE LT MAGNETO INOPERABLE ON RUN-UP. TROUBLESHOT AND FOUND CONTACT POINTS NOT OPENING FAR ENOUGH. NYLON CAM FOLLOWER FOUND MELTED AT CONTACT POINT ARM. CONTACT COMPARTMENT COVER HAS VENT HOLES THAT ARE COVERED BY INSTRUCTIONS IN MASTER SM X40000 S20/S200 . SUSPECT THAT LACK OF VENTILATION CONTRIBUTED TO SOFTENING OF CAM FOLLOWER EITHER THROUGH IONIZATION AND OR EXCESS HEAT. RECOMMEND OPENING VENT HOLES.