As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ENGINE RUNUP INDICATED A DEAD MAGNETO. REMOVED AND DISASSEMBLED MAGNETO HOUSING. FOUND ROTOR SHAFT SHEARED OFF AT BOTTOM OF CAM SLOT. A FEW CRACKED SHAFTS HAVE BEEN FOUND AT 500 HR INSPECTIONS. RECOMMEND CLOSE INSPECTION OF THIS AREA AT REPAIR AND OVERHAUL. (K)