https://youtu.be/5rCjZzJCe_4 bug ??

If you mean the suddendly flying car - it's a well known issue that barriers in most tracks have correct physics just from one side,while other side throws the car throug barrier. I suspect a shortcut in programming bakc then when it was made.
This is not an issue in rebuilt new Westhill or Rockingham,buy a licence to check it out!

He probably means the car in focus. Its wheels went through the ground and the car was stuck there.

Not really a message on topic, but what are textures you're using? Are they private?