The bug
When you place a recipe in the crafting field in the survival inventory and close the inventory in the exact same frame as you put the last item of the recipe into the crafting slots, a ghost item will be created upon reopening the inventory.
To reproduce
Limit your frame rate to 10 fps (or have a computer that is bad enough)
Open the survival inventory
Put a diamond block into the crafting field
Close the survival inventory in the same frame
Reopen the survival inventory
❌ There will be nine diamonds in the crafting result slot. They will disappear when trying to pick them up, but you can transfer them into the normal inventory by pressing shift while clicking on them. In that case they will act like usual ghost items and disappear after a while.
Original description
When I placed (for example) redstone block into inventory crafting and quickly closed it and reentered it, then redstone block moved into inventory, when nine redstone stayed in crafting; I can grab it into inventory, however it vanished while I opened a chest.
Here is my amatour video (recorded with phone sigh) in which I'm showing this "copying": https://youtu.be/XT62JKFs4es
Comments 5
Aha, was able to reproduce, but only if I manage to close the inventory in the same frame as I put the blocks into the crafting field, which is really hard if you have a good framerate. To reproduce this, I set my maximum frame rate to 10 fps. Also, if you don't use shift-click to take the "duplicated" items out of the crafting result slot, they'll disappear immediately.
Did this happen on a server or in single player mode?