Im currently fiddling with the car physics stuff and during testing I had a car wheel pass down through a terrain and it couldnt get back out. somehow the wheel hit the floor to hard and passed right through, I suspect its a similar thing? Does that sound like it?

Since setting the PH_FPS_MAX and fps lock on I have not seen the problem again.

Edit: Does anyone know why my car is floating though, I have a good 20cm relative clearence under each wheel? TIA for any reply