As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DEN - AFTER TAKEOFF WHEN RETRACTING LANDING GEAR EXCESSIVE NOISE AND VIBRATION IN NOSE GEAR AREA. EMERGENCY DECLARED, RETURNED DEN WITHOUT INCIDENT. AIRCRAFT REMOVED FROM SERVICE. FOUND LEFT NOSE GEAR ACCESS DOOR OPEN UPON RETURN. INSPECTED NOSE GEAR, WHEEL WELL, AND DOORS FOR PROPER OPERATION NO FAULTS NOTED. RELEASED ACTUATOR. SYSTEM GROUND CHECK NORMAL OPERATION.