As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT 241 BOS-MCO, AIR RETURN TO BOS DUE TO "AVNX MAU 3A FAIL" ON EICAS 15 MINS INTO FLT WITH ASSOCIATED EICAS MSGS. "AVNX MAU 2A FAIL" TEN MINUTES LATER WITH ASSOCIATED EICAS MSGS. MAU 2 PWR 1 & MAU 3 PWR 1 CB'S POPPED. REPLACED MAU 2-1 PWR SUPPLY AND MAU 3-1 POWER SUPPLY IAW 31-41-02. ALL INDICATIONS NORMAL.