Minecraft Version: 1.20.1
Mod Version: 1.2.1
Mod Loader: forge

Description:
Duplication glitch using Sculk Transmitter.

To Reproduce:
Steps to reproduce the behavior:
Fill a double chest with Shulker Boxes
Link to Sculk Transmitter
Go far away to deload the area
Use Sculk Transmitter and take a Shulker Box
Close the Sculk Transmitter
Use the Sculk Transmitter and there should be the Shulker Box you just took still in the chest

Screenshots:

Full Chest of boxes

Linking the Sculk Transmitter

Opening the Sculk Transmitter from very far away (~5k blocks), and taking a box out

Box reappearing in linked chest

Showing all boxes still being there

Additional context:
Can be infinitely repeated
Even when going back to the chest the boxes that were duped still exist along with the original box

Can confirm for fabric 1.19.2. Works with any item (I used diamonds).

fixed for forge in 6cd94ed

Fixed for Fabric 184004a