I have not experienced this problem before, but I have a toposurface that has been functioning normally. Today a part of my toposurface appears to have been sliced off, but the elevation points are still there (see first image). Additionally, if I move a point up, the toposurface does move with it, but its still offset some value. So this proves to me there isn't some void element that is cutting a part of my surface.
Anyone have any ideas?
