As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PERFORMED AN AIR TURNBACK AFTER TAKEOFF DUE TO AN EICAS MESSAGE OF GEAR DISAGREE AFTER RAISING THE LANDING GEAR HANDLE. THE LT GEAR STAYED DOWN AND INDICATED GREEN. THE CREW LOWERED GEAR HANDLE AND RECEIVED A NORMAL GEAR DOWN INDICATIONS. T/S IAW FIM 32-30-00-815-818. REPLACED LT DOOR-OPERATED GEAR SEQUENCE VALVE IAW AMM 32-30-05. OPS CHECK WAS GOOD.