Hello, so with the new "Bundle" item if you put an item in it and throw it in a cauldron of lava the item will double i.e I put in a stack of diamonds when I throw it in it will give me back 2 stacks of diamonds, this is only when you put it in the "Bundle" item and throw it in a cauldron of lava, this may be the case with normal lava as well, please check this bug out as soon ASAP as it is active and it is a sure way of duplicating any item on Minecraft java edition.

thanks and my best regards

RealDadwar - a Minecraft player.