As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS NOT GROUNDED: AFTER R4 SLIDE CHANGE, DURING EMERGENCY POWER SUPPLY UNIT TEST, FLIGHT ATTENDANT PANEL SHOWING "EPSU INT LOAD EME R FAULT MESSAGE. REPLACED EMERGENCY POWER SUPPLY UNIT AND ACCOMPLISHED A SATISFACTORY OPERATIONAL CHECK PER AMM 33-51-38.