When I drive around in a rover with chase view enabled, it sometimes moves by itself depending on the terrain. I would expect it to stay in the same relative angle to my car, i.e. when I set a classic 3rd person arcade racing cam, it stays that way. Instead it could be that I suddenly see my car from above...
I think it also happened to me while flying planes sometimes...
I will look into planes within the next days again.
Would it be better to clip the camera through terrain for cars instead of pushing it?