RTS NW Custom houses

[GomuGomu64]

I'll keep it short.

 

 

I made a mod that replaces the indoor parts of the Scrap-metal Academy and Houses with something more appropriate, but whenever I go to the edge of the houses(Behind the staircase, for example), I get this wierd glitch where everything inside the house (Including walls) dissapears, but a few items that are outside the walls are visible. The cell is fully navmeshed, and when NPCs walk to the same part, they "reset" and go back to the center of the house.

 

Here's my .esp : http://www.mediafire.com/?6ezm1p6nev96zu6

 

Any and all help is appreciated.