Survival mode:

Before placing an Empty shulker box, you can move it within your inventory or place it. Once it's been placed & mined, you cannot move it within your inventory or place it again.

Steps to recreate:

1. Load a game with an Empty shulker box in your inventory or hot bar (or move one there from your inventory or a chest).
2. Place it.
3. Mine it with a pickaxe & pick it up.
4. If it's added to your hot bar when picked up, you will not be able to place it and you will not be able to move it within your inventory.

• If you save & quit, you can place it and move it in your inventory when you reload the world, until it's been placed and mined again.
• If items are added to it after being placed, you can mine and place again. If all items are removed, you will not be able to place it again.