As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DIVERTED AND DECLARED AN EMERGENCY DUE TO RUDDER TRIM TO THE LEFT NOT RESPONDING WHILE USING AUTOPILOT. CREW HAD TO HAND FLY THE AIRCRAFT WITH CONSTANT LEFT RUDDER PRESSURE TO MAINTAIN CONTROL. LANDED WITHOUT INCIDENT. FOUND AND CLEANED DEBRIS IN THE RUDDER TRIM SWITCH. PERFORMED GROUND CHECKS WITH AUTO PILOT ON AND OFF. OPS CHECKS GOOD. MVF WAS SUCCESSFUL.