I've noticed that they have split the collision detection across several frames of the game. This stuff probably happens when the calculations go out of sync briefly.
The most obvious example is running down those weak wooden fences and small poles in cars or bikes, where the moment you hit them the car/bike will stop for a frame or two and then break the object and move along at the speed it had before the impact.
This leads me to believe that all of this weird stuff was done on purpose (a side effect of splitting the calculations) to make the game run a little faster at the cost of precision and accuracy. I'm fairly sure that all these things should become a lot more rare if not gone completely in the remastered version of the game where they shouldnt have to do all this to get it playable.