Destroying a shulker box using a piston or an explosion, or breaking it in Creative mode drops all of the items from the shulker box while not emptying it out, thus duplicating items.
How to reproduce:
Method #1:
Place a shulker box and insert any items into it.
Place a piston facing the shulker box.
Power the piston.
Method #2:
Place a shulker box and insert any items into it.
Place TNT next to the shulker box.
Light the TNT.
Method #3:
Place a shulker box and insert any items into it.
Switch to Creative mode.
Break the shulker box with your hand.
Linked issues
Comments 3
Can confirm, even when destroying the shulker box in creative mode, it duplicate the items from that shulker box.
Can confirm. This applies to every block or entity (e.g. boats with chests) that has a accessible inventory. The content drops when mining the block/killing the entity and duplicates when destryed with external sources like tnt or pistons.