As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) CREW REPORTED "A/P TRIM" MASTER WARNING FOLLOWED BY AN A/P DISCONNECT EVENT DURING DESCENT TO DESTINATION AIRPORT. AUTO PILOT WOULD NOT RESET/TEST. MX REVEALED A FAILURE OF THE ALTERNATE-AUTO TRIM PORTION OF THE STAB TRIM ACTUATOR ASSY. MAIN TRIM PORTION FUNCTIONAL. THERE IS 578 HRS, TIME IN SERVICE ON THIS O/H PART. STAB TRIM ACTUATOR ASSY REPLACED, FUNCTION TESTS NORMAL.