Hey - i'm creating a house mod and i've found a worldspace that provides a really good template or skeleton if you will for my cavern, but when i copy the worldspace the landscape beneath everything messes completely up and some gets lowered and some stays in place?!?!

Edit: It seems that the landscape is divided into squares and even though in the original worldspace these squares were aligned, when you copy it they become misaligned.
Also, my CK constantly crashes when i try to work in this duplicated worldspace, any help?