As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING HEAVY MAINTENANCE, DONT PASS TEST BATTERY EPSU EMERGENCY POWER SUPPLY UNIT 12WL IN PASSENGER CABIN; (REF AEROMAN NR 2021-387113 WO 2021 196/1) R & R BATTERY EPSU-EMERGENCY POWER SUPPLY UNIT 12WL IN PASSENGER CABIN IAW AMM 33-51-38-000-002-A AND AMM 33-51-38-400-002-A AND PERFORMED OPERATIONAL CHECK IAW AMM 33-51-00-7.