You don't just have double jetways: you also have jetways in the air. Jetways in the air are caused by with conflicting altitudes. and can be fixed in GSX with the parking customization page, by clicking the small "airplane" icon on the top right of the window, which says "Ground Elevation".
However, this will only fix the "jetways in the air" problem, not the double jetways problem, which is caused by conflicting .BGLs for the same airport.