As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF, A GEAR DISAGREE WARNING MESSAGE. CAPT REPORTED A RHYTHMIC THUMPING FROM NOSE AREA. FLIGHT CREW EXTENDED THE GEAR AND RETRACTED WITH THE SAME RESULTS. GEAR WAS EXTENDED AND THE AIRCRAFT RETURNED TO FIELD WITHOUT INCIDENT. FERRIED AIRCRAFT, MECHANIC IS TROUBLESHOOTING. MECHANIC REMOVED AND REPLACED THE MAIN LANDING GEAR RUNAROUND BYPASS VALVE. OPS CHECK GOOD.