Brush Errors

Those strips there are essentially behaving like a nodraw, going off into the abyss and drawing what's behind it- in this case, spawn room.

The kicker is though, there's no such strip in hammer, you'd think there's something wrong with the brush. However, I haven't touched either of the brushes for many compiles, and it was fine until a second compile of the same vmf.

Anybody got any ideas why this is happening?

After doing some investigating, the narrow brush in the second image with the light texture is the cause... But I don't know why this happens.

When said brush is a world brush, the two blue brushes near it behave fine. However, when the narrow brush becomes a func_detail, then this problem happens.

...So what's the reasoning to this strange behaviour?