Pretty straightforward, there's a car sized gap in the rock that shouldn't be there, and it's great for getting stuck in.
Which version of Grip were you using :
When does this happen : Racing
On which track did it happen : Industrial
On which speed did that happen (if related to physics) : N/A
How often does this happen : ALWAYS
How to replicate the steps (if reproducible) : Drive into the hole
More details : It's a hole. In the fabric of the world. Perhaps I should call a doctor?
Your specs : viewtopic.php?f=19&t=662
Any screenshot, or link to a video showing the bug :