As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS NOT GROUNDED: DURING PERIODIC SERVICE CHECK EMERGENCY LIGHTS EMERGENCY POWER SUPPLY UNIT TEST FOUND BATTERY/ EMERGENCY POWER SUPPLY UNIT 13WL AFT LEFT CLASS 1 MESSAGE. REPLACED EMERGENCY POWER SUPPLY UNIT 13WL AND ACCOMPLISHED A SATISFACTORY OPERATIONAL CHECK PER AMM 33-51-38.