Had not realized this was a duplicate, please see original report.

When an item is given to an Armor Stand, and that Armor Stand is given invisibility, the item it had will float relative to the player's position.

This item will remain until you unload the Armor Stand, remove the item, destroy it, or the invisibility ends.

Steps to reproduce:

1: Place Armor Stand.

2: Give The Armor Stand a Mainhand Item (e.g. Bow)

3: Run This Command: /effect @e[type=armor_stand] invisibility 10 0

4: Item Moves With Player