I've got smooth and flat kinda curved wall object.
Big model length of 30cm and 14cm high,11 hours printing.
There is NO issues with .stl or g-code. I've tested it in Repetier and Simplify3D g-code preview.
But there is issue during print

At the middle of printing every layers just SHIFTed or something like that by ~1mm.
There is result on a picture.
How ?
Why it's happened ?
How to prevent this in future ?