As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING HEAVY MAINTENANCE, FAULT EPSU-EMERGENCY POWER SUPPLY UNIT 15WL IN PASSENGER CABIN (1EA); (REF AEROMAN NR 2121-148055 WO 2021 120/1) R & R EPSU-EMERGENCY POWER SUPPLY UNIT 15WL IN PASSENGER CABIN (1 EA) IAW AMM 33-51-38-000-001-A, 33-51-38-400-001-A. AND PERFORMED OPERATIONAL CHECK OF THE EPSU BY BITE CHECK IAW AMM 33-51-00-710-001 TEST IS OK.