As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
GEAR DISAGREE WARNING AFTER GEAR SELECTED UP AFTER TAKEOFF FOLLOWED QRH. AIR RETURN DUE TO MKE INDICATED RED X-MARKS 10 SECONDS AFTER GEAR RETRACTION. FOUND NLG OLEO STRUT LOW REF SUPP 08-067 SERVICED NLG SHOCK STRUT WITH OIL AND NITROGEN PER AMM 12-12-32 TR 12-122. OPS TEST LNDG GEAR EXTENSION REF GOOD PER AMM 32-30-00.