The Bug
If you Ctrl + Pick block on a campfire that has food cooking on it, the copy of the item in the inventory will keep updating its NBT during the time the actual original block is cooking food.
When the original campfire block has finished cooking, if the copied item is placed it will instantly drop the (also copied) food on it.
During this cooking time the copied item also heavily shakes in your hand (or is constantly off-screen if your computer is fast). This part of the issue is tracked in MC-143614
How to reproduce
Place a campfire
Right-click it with raw food to start cooking it
In creative mode, press CTRL while you middle-click the campfire with an empty hand (this copies the block along with its NBT)
Wait until the placed campfire has finished cooking and a cooked food item drops from it
Now place the copy from your hand next to it
→❌ Notice a second cooked food item instantly drops from the new block
Linked issues
relates to 1
Comments 24
Related by MC-143614, as explained in above message
Additionally, the held item model of the copied campfire is somehow 3D animated, until you open the inventory, at which point it becomes a static 2D item again like from creative inventory. This animation is only visible from first-person view and not when changing the camera to third-person mode.