As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DCA - FLT 1837 - EN ROUTE BOS-DCA, SHORTLY BEFORE LANDING DCA DETECTED MAIN GEAR WARNING IN COCKPIT. MAIN LANDING GEAR SLOW TO EXTEND. LANDED DCA WITHOUT FURTHER INCIDENT. REPLACED MAIN GEAR PRESSURE REDUCER. SYSTEM GROUND CHECKED NORMAL OPERATION. (M)