When you save a structure with shulkers in it, the shulkers will appear at the position in the world were you saved the structure rather then were you loaded it.

The reason why this happens is because Shulkers have additionally to the Pos:[] -tag as well APX, APY and APZ which keep track of the Shulker's position in the world.

If you open the *.nbt-File with an external tool and remove these tags, it will work as expected.

For testing you can use shulkerTest.nbt in the attachments. It will spawn the Shulker always at 0, 70, 0.