Armor Stands disapearing when in different chunk from them

When summoning an array of armor stands half-way into the ground in my creative world, they first look like this: http://prntscr.com/74me3i (There is an invisible skeleton in there too, but it doesn't disapear), but when moving to the left slightly while still looking at them, and moving into a seperate chunk, the armor stands seem to disapear like this: http://prntscr.com/74me6r and I am unsure why that happens. When moving back to the original position, however, the armor stands reappear.