As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
GEAR DISAGREE WARNING ON APPROACH. PUT GEAR HANDLE DOWN AND NOTHING HAPPENED. FLAPS WERE AT 30 DEGREES AT THE TIME, AFTER THE GO AROUND WE RETRACTED TO 20 DEGREES THE GEAR SUDDENLY EXTENDED. REPLACED LANDING GEAR SELECTOR VALVE IAW 32-32-10. OPS AND LEAK CHECKS GOOD, PN ON/OFF 53340-9, SN ON NGL/1574/06, SN OFF NGL/1557/06.