I downloaded a map with invisible armor stands and I noticed that whenever I placed an armor stand near them, all the items from the invisible armor stands visually appear on the armor stand at once. And breaking it causes what is down below. The items follow you in the axis you move but not look. When you get out of range of the invisible armor stands the items disappear and reappear depending on location.
How to reproduce.
1. Place and armor stand and effect it with invisibility with commands and make the particles invisible as well, give it an item before you do this however.
2. Do this about 3 times with 3 different stands and put different items on them.
3. Place a visible stand near the others, if you remember hopefully.
4. Voila, you now have the weirdest armor stand ever, break it and you get a visually floating occurrence of items, that follow you until you move far away.