As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
RIGHT MAIN LANDING GEAR FAILED TO EXTEND FOR LANDING AT DEN. USED MANUAL EXTENSION AND LANDED WITHOUT INCIDENT. *S/D* FOUND BOLT BACKED OUT OF LINK (NUT MISSING) AT RT MAIN LANDING GEAR DOOR OPERATED SEQUENCE VALVE. REINSTALLED BOLT AND NUT. OPS CHECKED GEAR, SYSTEM OPS NORMAL.