Thank you for the replies @Oldeseadogge and @StuffyMarx
I just figured out what was causing that but that creates a new puzzling question. The cause was the lot type was affecting the camera. I placed that on the Chateau Peak lot in DSV. In my rush placing it I didn't change the lot type when it asked me too while I was placing it so it was still set for residential instead of generic. Once I changed it that solved the disappearing walls thing.
Now that makes me wonder why does the lot type matter? The way the problem shows itself it's like it's an LOD issue. It's like the game has a limit on how many polygons can be viewed or rendered according to the lot type chosen. In these first two shots there isn't a huge amount of detail so I can get the camera fairly close to ground level before things start disappearing...
https://i.imgur.com/f8aJv6B.png
https://i.imgur.com/u5MzmG2.png
...but when I turn it around and aim it towards an area with a crazy level of details things disappear with the camera still at a high angle.
https://i.imgur.com/cXsL8F3.png
https://i.imgur.com/P3BqkRQ.png
