As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS IN BASE MAINTENANCE: INOP EPSU-EMERGENCY POWER SUPPLY UNIT 13WL INCLUDING BATTERY IN PASSENGER CABIN. REPLACED EPSU-EMERGENCY POWER SUPPLY UNIT 13WL (AALA202403209537) INCLUDING BATTERY (AALA202403209446) IN PASSENGER CABIN.