As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN)DURING ROUTINE INSPECITON AND RETORQUE OF THE MAIN FLAP CARRIAGE SPINDLE RETAINING NUTS, THE #1 T.E. FLAP SPINDLE NUT RETAINER HAD FALLEN OUT OF POSITION AND DAMAGED THE STRUCTURE. INSPECTION REVEALED THAT THE RETAINER NUT LOCK BOLT HAD SHEARED DUE TO HYDROGEN EMBRITTLEMENT OF THE BOLT. REPLACED.