aerosoft Zûrich professional default jetway config via GSX ctrl+F12 or just ctrl+J
Ok, then you can be sure that GSX doesn't have anything to do with it.
When a scenery has SODE jetways, the door configuration used by SODE is being sent from GSX, using its own airplane configuration data but, on a scenery that used default CTRL+J Jetways, GSX doesn't have anything to do with it (other than sending the CTRL+J command for you), and the position where the jetways docks to it's controlled only by the [Exits] sections of the aircraft.cfg file.
This doesn't mean the aircraft.cfg file might be "wrong".
Default jetways sometimes are unpredictable, which is why most new sceneries are switching away from them, and use SODE, which in addition to be more flexible (allows for multiple jetways on a single parking), is way more reliable and predictable, in addition to be also easier to develop for.