As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE AT GATE, GROUND PERSONNEL PULLED GROUND POWER WHILE STILL IN USE CAUSING THE EMERGENCY LIGHTS TO ACTIVATE. ALL LIGHTS ACTIVATED EXCEPT THE FORWARD CEILING EMERGENCY EXIT SIGN. MAINTENANCE REPLACED THE FORWARD CEILING EMERGENCY EXIT SIGN WITH NO FURTHER DEFECTS NOTED.