As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
EITHER AUTOPILOT WHEN ENGAGED AC INITALLY PITCHED THEN TRIMS NOSE DOWN UNTIL REACHING A/P LIMIT AND BEGINS UNDEMANDED DESCENT. RIGGED MECH PITCH FEEL/ TRIM ASSY IAW MM 27-41-17. (INPUT AND SERIES TRIM PUSH RODS WERE OFF) CKD RIG OF A/P STAB SERVO IAW MM 22-11-05. PERFORMED TRIM AUG TEST IAW MM 22-18-00. ALL CHECKS GOOD. (K)