Bug in Item hold in a Armor Stand

Before i discover this bug, i just doing some experiment, my plan is to have a floating book up to the bookshelf block, my trick is to place a armor stand above of a slab block, then the arnor stand will hold a book, then i pose the armor stand like it rising the book and staring it, after that i pushed a bookshelf block to the armor stand using piston, then i gave a invisibility effect to armor stand and i am wondering why the item that the armor stand hold keeps following to the player camera sight , i remove the invisibility effect and it stops following and the item returned to the armor stand and it holds it, i try holding it another item and gave invisibility effect and the bug happens again and stops after the invisibility effect is gone, i try put the armor stand on a normal block and do the same thing, the bug still happens and stops after thr invisibility effect is gone , there is no command blocks running in the world, please fix this bug as soon as possibe, thanks