The problem doesn't have anything to do with GSX. It's likely caused by a ground elevation conflict, likely caused by OrbX vector.
- If you have OrbX vector, be sure that airport is selected in the AEC utility.
- In the GSX scenery customization page, press the small Airplane icon on the top-right of the window ( when you are parked on this airport ), which will usually fix the elevation problem caused by conflicting AFCAD files that set a different elevation than default.
