The only other thing I can think of is maybe the truck colliding on itself. There isn't but the wheels, do stop on those edges for some reason.
Crazy Taxi was one of the inspirations for this game. Running over zombies were going to be in the game, the feature is actually still in the game but disabled.
But I removed the town because of the known issue but I do plan on finishing this game for sure. Glad you enjoyed it!