GSX vehicles driving through scenery elements is entirely normal, and has explained so many times on the forum: the GSX vehicles are entirely "blind" to the outside scenery, the only thing they see is the taxiway/paths layout of the scenery AFCAD, at least in case of the vehicles that comes from far away, such as the catering truck, the arriving baggage loaders, the fuel truck or the follow me car.
IF the AFCAD is well designed, with proper vehicle paths that wouldn't force GSX to use airplane taxiways instead, the chances for clashes with other vehicles or AI airplanes should be minimal, and they surely shouldn't drive through scenery elements, unless the AFCAD file has been made so badly, that features paths running through scenery objects.
Assuming, of course, there isn't an AFCAD conflict. If you are using an AFCAD that is not correct for the scenery (common with AI Traffic products: their own AFCADs interfere with the ones that come with the airport), all bets are out, and everything can happen...
This, related to GSX vehicles that comes from far away.
For GSX vehicles that are created on the parking, they don't use the AFCAD layout but, they still can drive through each other and, of course, even this is not obviously a "bug", but a clear and sensible design decision. GSX vehicles are not aware of each other. Yes, it would be nice if they could but, this would put a very large strain on the simulator and Simconnect, potentially affecting all the other addons in the process because, GSX would then have to monitor, constantly, the actual position of each and every vehicle in the airport, both its own, but also the other ground traffic.
And, even if we couldn't hypothetically accept that performance hit and the likely heavy stuttering that we would create to the simulator (we can't), having all vehicles being able to yield to each other, would create a whole new class of bigger problems, like traffic deadlocks over the usually cramped space on the apron.
But it gets better: suppose you are following the GSX follow me over a long taxiway with no exits and, while you are in the middle of it, an AI goes there in the opposite direction. What could GSX do to prevent this ? Simply NOTHING. The only way to have everything working, would be that GSX would have to handle the ENTIRE traffic of the airport by itself so, that AI wouldn't even start to move (it could be delayed, for example), if its own calculated path ever conflicted with any of the paths taken by the GSX vehicles. That would be the only way to have the whole ground traffic foolproof, but you can surely realize why this is not feasible.
What CAN be done, instead, is to play with the GSX customization page, and change the vehicles starting positions. Their interaction is what can cause AND prevent clashes between them. And of course, with the same method, you can prevent they would drive through static scenery object that, as I've said, you can see, but GSX cannot.