As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
L-1 DOOR MADE A POP SOUND ON TAKEOFF. AIRCRAFT STOP PRESSURIZING. DOOR LIGHT SHOWED THE L-1 DOOR WAS CLOSED. AFTER RETURNING TO THE GATE, L-1 DOOR FOUND NOT COMPLETELY CLOSED. CLEANED AND LUBED ROLLERS AND CRANKS IAW 52-11-00. OPS CHECK WAS GOOD. INSPECTED DOOR AND JAMB IAW 52-11-00. NO DEFECT NOTED.