GSX vehicles don't know anything about visible obstacles in the scenery, their only reference of the outside world is the AFCAD so, if the scenery is crammed with ground objects, it's likely you'll see something like that.
It's usually not a problem with default airports, because the default ground vehicles can be easily removed automatically on the chosen parking (and GSX does that) and the more recent sceneries we made (KDFW, KLAX) have been made in a way that their static ground objects are also recognized by GSX and removed but, for 3rd party airports, your only choice could be using the "Customize parking position" option, and play with the parking radius parameters, to at least lessen the most obvious problems.