The problem now is, that GSX only works in case the aircraft stands around 20 meter ahead of its designated Position (in the middle of the terminal building). Has this something to do with the so called AFCAD-file ?
Of course it's related to the AFCAD: that's the only data GSX takes from FSX.
First, you should check if GSX is using the new AFCAD you added, which can be done by looking at the parking customization page, the name is listed in the top of the dialog box.
If the scenery used is not the one you installed, assuming you installed it on a layer in the Scenery Library higher than the one currently in use, it's POSSIBLE this AFCAD is not "self-contained" ?
Some AFCADs, especially freeware ones, are not supposed to be used alone, but are only "enhancements" of the default ones. While FSX supports this, and is able to take data from multiple files at once, GSX doesn't support it, and requires the AFCAD in use would include all parkings and a taxiway layout. An AFCAD that, for example, only adds new parkings or moves existing ones cannot be used by GSX, which will continue to work with the default one.
