ok, there is one more thing I forgot to mention. When I move the aircraft (in this case the 747) closer to the (double) jetways, then GSX will also recognize for example one of them. And of course then, the aircraft is not standing on the yellow line anymore. Also, when going into the Edit Park Position Feature of GSX, it shows that 2 SODE Jetways come with this gate.
So I figure it can't be the names/labels because then, GSX wouldn't recognize them at all and also not show them in the edit function?