As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) ALTERNATOR WS REMOVE TO CHECK FOR INSTALLATION OF NUT AND SPLINE DRIVE. COTTER PINE WAS BROKEN AND NUT WAS BACKED OFF ON SPLINE. BOTH THE NUT AND COTTER PIN WS FOUND INSIDE THE ENGINE SPLINE GEAR. ALTERNATOR WAS SENT TO MANUFACTURER FOR OBSERVATIONS.