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 PS CHECK OPERATIONAL CHECK OF THE EMERGENCY POWER ASSIST SYSTEM BATTERY, EMERGENCY POWER ASSIST SYSTEM DOOR R4 INOPERATIVE. REMOVED AND REPLACED EMERGENCY POWER ASSIST SYSTEM BATTERY PACK AT DOOR R4 AS PER B777 AMM 52-11-20.