As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
UNSCHEDULED LANDING DUE TO A RUDDER TRIM IRREGULARITY. REPLACED RUDDER TRIM ACTUATOR, AND RUDDER TRIM CONTROL MODULE. CHECKED WIRING FROM D3116 TO D2932. ALL WIRES CHECKED GOOD. RUDDER TRIM MODULE WAS CONFIRMED BAD IN THE SHOP. THE SWITCH HAD AN INTERNAL FAILURE CAUSING INTERMITTENT OPERATION.