As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS NOT GROUNDED. WIRELESS EMERGENCY LIGHTING SYSTEM HAD SEVERAL AIRPLANE HEALTH MONITORING ALERT MESSAGES. REMOVED AND REPLACED WELS CONTROL UNIT BATTERY IN THE OVERHEAD FLIGHT CREW REST AREA IAW AMM B787-A-33-51-07-26T-941A-D. OPERATIONAL CHECK GOOD.