Wall won't render but its there in hammer

[Incredible Donk]

I'm not sure what to do about this. Both are brush entities and there are no area portals near by.

 

[nesman]

is your compile failing?

 

[Incredible Donk]

I ended up deleting the afflicted brushes and props and undoing said delete which ended up fixing the issue. I don't know why it happened but hey it isn't an issue anymore.