Now this is embarrassing. I had 'disable staircases' checked! To be honest, i thought you could only disable staircase for the rear of the aircraft when there is a moving walkway connected to the front but not when the aircraft was on the apron. I see what you meant when you said "have you customized it" meaning GSX services at that position, i thought you meant the aircraft CFG. Ah well, fixed now. Thank you for being so patient.