As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CRUISE RECEIVED ANVX MAU 3B FAIL AND SPOILER FAULT MESSAGES. RAN QRH AND RETURNED TO ORD. DECLARED EMERGENCY, LANDING WAS UNEVENTFUL. MAINTENANCE REMOVED AND REPLACED NIC PROC 6, THEN LATER REPLACED THE POWER SUPPLY 2 IN MAU 3 AS PRECAUTIONARY.