Generally, when I race a course at least 3 times, it happens.
I use to collide and jump while flipping (key-button 't')
Here are the screen shots, (i couldn't make it in fullscreen...)
You can see in the third picture that the traces are in the air, plus there is many tracks that don't belong here. As if it as drew multiple time.
I modified some Speed, Brake, etc. variables but that should be ok...