I'll copy here the answer you already got on the MSFS forum:
the problem is not GSX, of course, the problem is that lamp post shouldn’t be in the middle of a vehicle road!
Now, whether this is a mistake in the scenery, or a conflict with another scenery, I cannot possibly know but, clearly, that lamp post shouldn’t be there and, even if you didn’t use GSX, the small service car would have crashed into it.
The reason why the bus is floating, is because the ground altitude there has been altered by the presence of the car crash bounding box and, considering you said that car is a static vehicle, if this is the case, I wonder what would be the reasoning of placing a static car on a vehicle road, near a lamp post that shouldn't even be there.