More trouble my way

[Ob1KenobiGH]

Ok, I'm trying to make a grocery store. I am making the cash register manually by cleaving sectors and deleting. However, Sometimes when I delete a sector half the floor goes by-by.
WHAT THE BLOODY $%!! IS GOING ON?

[GuNbOy]

first of all this isnt a COG question, so it belongs on the editing board.

second there are many things that can make it look like that, make sure your surface has less than 24 vertecies
and also it could be that the surface is either non convex or non-planar

use teh CONSISTANCY CHECKER and it will tell you these things!