Probably these parkings are just too close together, and FSX can't always decide where the airplane is parked, because they probably overlap. It might be possible to fix it by reducing the parking size (maybe), but this would affect the kind of airplanes that are allowed to park there.
It's all done in the AFCAD, though so, we might have a look at it, when Harpsi will finalize his own version, so we can work on the improved one already.
