TGEA 1.8.1 $backbuff problems

Hello everyone! I am trying to make some effects that use the back buffer ($backbuff). To test the $backbuff texture, I applied it to the default buggy. When I drive around, you can see the texture showing the same thing as the camera, but sometimes, the texture doesn't update in a since and show what is in the camera. It just stays the same. When you turn the camera in certain angles, it does this. The back buffer needs to have the correct texture at all times. Why is this?