That's a good question. Well... Unfortunately I have no idea. Maybe another member can help you with this.
I am guessing those were purposefully made hacks by developers. I mean by having those stalled cars, the result of the game could change. Or it's possible it could be simply a bug.
Maybe I'm wrong, but I don't know... I think the possibility of being a bug actually is something very remote to have happened.
Bugs are easy in games. Or possibly it could be developer hack too. They often play with the games config and the stuff.So it is possible that they have done this. I am not sure though.
Yes, unfortunately bugs are more common than they should be and as most people don't care about them the developers seem to get relaxed about it.
There may be some patches that may get released. But that is all about it. I don't have much expectations from games these days. The reason being some of them end up updating a lot.