You don't say which scenery you use.
If the scenery use default jetways (CTRL+J), as explained in the manual and so many times on the forum, GSX doesn't have any control over them.
They are moved BY THE SIM, and the ONLY thing that affects their position, is how they are modeled and the [Exits] parameters in the aircraft.cfg file. NOTHING in GSX can change how a default jetway works.
If, instead, the scenery use SODE jetways, their positioning is controlled by the GSX doors configuration, but ONLY when you call them from the GSX menu. If you call them from the SODE menu instead, they are controlled by the airplane doors configuration in the SODE internal airplane database.