Anitportal Volume not working in-game

[Dryn]

For one of my maps, I have a two high detail areas seperated by a _very_ important antiportal [with a hallway to the side]. In ued, the antiportal volume is perfect; occludes just as it should without question; however, when I run the game directly, its as if this antiportal simply isn't there. I've tried different proportions [always a simple 'cube' brush, nothing fancy, nothing concave, no sheets], and doubled checked to make sure the volume doesn't intersect subtracted space. Has anyone run into a similar problem where one antiportal out of many simply doesn't seem to exist ingame?

Thanks in advance for your help

 

[Hourences]

make sure it always touches as many zones as possible and thus also touching substracted space else the zone optimisation will hide it and so it wont work

 

[Dryn]

Thx for the reply, will make sure it touches subtracted space... though I find it extremely odd as I have used literally hundreds of antiportals [not in just this one map ], always outside BSP space, with 0 issue until just now.