As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) DURING ROUTINE MAINTENANCE, NEITHER STAB TRIM CHANNELS WOULD ENGAGE. AFTER COMPLETING SPOST TEST, FAULT "H STAB/MCU/ACOFF/PHASE MISSING CH1" AND "H STAB/MCU/ACOFF/PHASE MISSING CH2" DISPLAYED. CHECKED AC SERVICEABLE ALL THE WAY TO THE H STAB ACTUATOR MOTORS. MCU (MOTOR CONTROL UNIT) FOUND TO HAVE SUFFERED A TOTAL FAILURE. BOTH CHANNELS U/S.