That means that there is something wrong with the world borders. There is a Leak in the world. It has nothing to do with your models. Find the leak by opening the Point file of your map. It should tell you were it is.
Edit:
Also no one can fix the problem of the map with the BSP file, we...
about 2 years ago there was a horrible accident involving vehicles and there was alot of police cars and ambulances and fire trucks. This happend close to were i live. They called a LifeFlight Helicopter and it landed Right Behind my House! I could see it from the top floor. It was only a few...