Shulker Box Dupe

I found a dupe in which to preform it you have need to have a shulker box and 2 players present, how you preform it is that you need to first place the shulker box down and player 1 needs to place the items they want to dupe in slot 1 of the shulker box, then while the items are in the shulker box player 1 needs to hover over them with their mouse cursor and start spamming the key “1” very fast as player 2 must start breaking the shulker box with their hand and they must break the shulker box, there is about I would say a 10 percent chance of the item duping but I managed to dupe about 1- 128 diamonds in the span of 11 minutes.