The inventory interface of the Supply Scamp does not automatically close in certain circumstances (such as when the Supply Scamp is unloaded or is too far away from the player), which can lead to issues with item duplication.

Steps to Reproduce:

1. Place the item you wish to duplicate into the Supply Scamp's inventory.
2. Open the Supply Scamp's inventory interface.
3. With the inventory interface still open, allow the Supply Scamp to enter the Nether Portal.
4. Once the Supply Scamp has entered the Nether, take out the previously placed item from the inventory and close the interface.
5. Subsequently, enter the Nether Portal yourself. In the Nether, you will find Supply Scamp with the same item still in its inventory.