As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: AFT EMERGENCY POWER SUPPLY UNIT FAILS SYSTEM TEST DUE TO INTERNAL AND EXTERNAL FAULTS. MAINTENANCE ISOLATED ISSUE TO THE L2 DOOR SLIDE AND REPLACED IT PER TASK CARD 26L00025011. A SATISFACTORY OPERATIONAL CHECK OF THE EMERGENCY LIGHTING SYSTEM WAS ACCOMPLISHED.