As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT IN BASE MAINTENANCE: DURING TEST OF PTP PANEL 110RH (NEXT TO FAP PANEL) RECEIVED "EPSU INT LOAD EMER R" MESSAGE. ON EPSU RH (12WL) SIDE "INTERIOR LIGHTS FAULT" IS ILLUMUNATED. MAINTENANCE REPLACED EMERGENCY POWER SUPPLY UNIT 12WL (AALA202303209220) AND BATTERY (AALA202303204015) PER AMM33-51-38. A SATISFACTORY OPERATIONAL CHECK WAS ACCOMPLISHED.