As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
STAB TRIM & MACH TRIM DISCONNECTS ON APPROACH, ONLY WHEN FLAPS LOWERED AND CAPTAIN TRIM CONTROL SWITCH USED. COULD NOT DUPLICATE ON GROUND. PERFORMED CONTINUITY, RESISTANCE CHECKS IAW ESPM 20-12-0 AND WM 27-41-00. NO DEFECTS NOTED. REMOVED AND REPLACED MCU IAW AMM 27-42-05. OPS CHECKED GOOD.