As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT 2028, DCA-BOS - AT 20,000FT THE CREW RECEIVED A SLAT/FLAP FAIL MESSAGE. THE CAPTAIN DECLARED AN EMERGENCY WITH THE TOWER. AFTER PERFORMING QRH PROCEDURES THE LIGHT WAS EXTINGUISHED. THE CAPTAIN CANCELLED THE EMERGENCY AND THE FLIGHT LANDED NORMALLY.