New geometry vanishes in game

[Deantendo]

Hi Folks,

 

Having a strange problem i can't figure out.

If i create a new model for the game, it goes in fine, shows just fine, snaps, has correct mats etc..
But if you walk too close or look at it from certain angles it just vanishes.

 

I get the same problem adding new verts to existing vanilla geo, but not altering existing verts.

 

ANY help appreciated. I want to make so many things to go in-game but this is obviously a total show-stopper.