There's nothing to fix here and it's not a GSX bug. The initial placement of the vehicles is taken by reading the parking radius as defined by the airport, so maybe the problem is the airport defined a radius to small to that parking spot.
This can be fixed in two ways:
- By changing the parking radius in the airplane customization page, which is the easiest method
- By placing all vehicles starting positions individually, which is what most creators of GSX profiles usually do.
You might want to check if there's already a GSX profile for that airport, so you won't have to create your own.