As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PDX - ON FLIGHT 2510 IN CRUISE, RECEIVED A STAB TRIM MESSAGE, AND A MACH TRIM MESSAGE. RETURNED TO PDX AND ACCOMPLISHED A UNEVENTFUL LANDING. MAINTENANCE REPLACED THE HORIZONTAL STABILIZER CONTROL UNIT (MCU). OPERATIONAL CHECK FLIGHT TESTS GOOD. AIRCRAFT RETURNED TO SERVICE.