As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: BOTH AFT EXIT SIGNS BLINKING RAPIDLY, ALSO BOTH SLIDE ARMING SIGNS BLINKING ON DOOR/OXYGEN ELECTRONIC CENTRALIZED AIRCRAFT MONITOR. REMOVED AND REPLACED EMERGENCY POWER SUPPLY UNIT (13WL) OPERATIONS CHECKS OK PER AMM 33-51-38-400-001-A.