Polyobject Door issues.

I was making a wad, and i wanted to use a sliding polyobject door. I've made these doors before with no problem. but this one gave me issues. At a certain angle, some of the textures would become invisable, allow me to see right through the thing. I have no idea how to fix this. I tried remaking the thing, moving it, etc. All of that did no good. Is there something wrong with the nodes or what?

Perhaps This could be of assistance to you.

No....it's not bleeding. the poly object is disappearing all together. I know there is a node building made for Polyobjects; ZDBSP i believe? But i cant find it o_o.

http://www.zdoom.org/files/utils/

Ok, i managed to fix the proble, I just deleted all the polyobject, the unused secotr it's in, and all the sectors that was touching the poly when in game, then rebuilt the thing. I idea what was wrong, though. O_o