As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
RUDDER TRIM FROZE DURING CRUISE FLIGHT. OPERATED NORMAL AT LOWER ALTITUDES. MAINTENANCE PERFORMED THE REQUIREMENTS OF NTO LETTER FOR TRIM ACTUATOR LUBE. OPS CHECK FLIGHT WAS UNSUCCESSFUL. AIRCRAFT DIVERTED. MAINTENANCE REPLACED THE RUDDER TRIM ACTUATOR.