As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PULLEY GUARD PIN, PN NAS427K-20, MIGRATED OUT OF THE LOCKING POSITION OF THE PULLEY ASSY FOR THE RUDDER TRIM CABLE, CAUSING A CONDITION THROUGH THE VIBRATION OF FLIGHT AND GROUND OPERATION OF THE CABLES COMING OFF OF THE PULLEYS AND CROSSING FROM ONE PULLEY TO THE OTHER. THIS SAME DEFECT WAS FOUND ON OTHER ACFT DURING MODIFICATIONS AND FOUND IN SEVERAL DIFFERENT LOCATIONS OF THE ACFT, MAINLY THE UNDER FLOOR AREA. THE LOCKING FEATURE OF THE PULLEY GUARD PIN SEEMS TO BE THE ISSUE HERE AS IT DOES NOT TAKE MUCH PRESSURE TO DISLODGE THE PIN WHEN INSTALLED.