As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE FLIGHT CREW REPORTED THE AIRCRAFT PITCH NOSE UP/NOSE DOWN ERRATICALLY WITH AUTO-PILOT CONNECTED. AUTO-PILOT TRIM NOSE UP/ NOSE DOWN MESSAGE ILLUMINATED. OPERATIONS WERE CONTINUED PER MEL. THE MAINTENANCE VENDOR DETERMINED AN AUTOPILOT SERVO WAS AT FAULT AND WAS REPLACED WITH AN OVERHAULED UNIT. OPERATIONAL CHECKS WERE SATISFACTORY AND THE AIRCRAFT WAS RETURNED TO SERVICE.