As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT IN BASE MAINTENANCE: EMERGENCY POWER SUPPLY UNIT BUILT IN TEST EQUIPMENT TEST FAIL. EMERGENCY POWER SUPPLY UNIT BUILT IN TEST EQUIPMENT TEST WAS PERFORMED IN MAINTENANCE CONFIGURATION. OPERATIONS CHECK FAILED. PERFORMED EMERGENCY POWER SUPPLY UNIT BUILT IN TEST EQUIPMENT TEST IN FLIGHT CONFIGURATION PER AIRBUS A321 AMM 33-51-00. OPERATIONS CHECK GOOD.