As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LAX INFLIGHT - MACH SPEED TRIM INDICATIONS AT 16000 FEET. AUTOPILOT WAS OFF AIRSPEED ABOUT 270 KNOTS INDICATED AIR SPEED. RETURNED TO LAX AND LANDED WITHOUT INCIDENT. REPLACED RIGHT STABILIZER TRIM ASYMMETRY MODULE AND RIGHT STABILIZER TRIM CONTROL MODULE BRAKE PRESSURE SWITCH (MPN 10605525). SYSTEM GROUND CHECKED NORMAL OPERATION.