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 LEFT HAND FORWARD SLIDE CHANGE, EMERGENCY POWER SUPPLY UNIT SYSTEM TEST RESULTED IN FAULT MESSAGE. LEFT/EMERGENCY POWER SUPPLY UNIT (12WL) EXTERNAL RIGHT FAULT. REPLACED EMERGENCY POWER SUPPLY UNIT (12WL).