As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AUTOPILOT MISTRIM (E) ILLUMINATED AT FL310 AFTER START OF DESCENT. MANUAL PITCH TRIM WAS FROZEN. BEGAN WORKING AFTER DESCENDING INTO WARMER ALTITUDE FL120. MAINTENANCE REPLACED THE LEFT AND RIGHT PITCH TRIM ACTUATORS. REMOVED ACTUATORS SENT FOR EVALUATION. A SUCCESSFUL OPS CHECK FLIGHT WAS PERFORMED. AIRCRAFT WAS RETURNED TO SERVICE.