Shulker box Duplication glitch

Players can use shulker boxes to duplicate items. There are videos of it on youtube. I found this out from one of my players duplicating 17650 diamonds and selling them along with giving them away to players. I can provide a log of him placing the shulker box. I assume this has to do with lag or how the shulker box acts when picked up via the enderchest. Attached is a coreprotect log (logging plugin) of a player placing and removing a shulker box. Along with here is a link of how someone does it: https://www.youtube.com/watch?v=P2eUSvjrdeE