The bug
This bug creates a piston head ghost block. It must be done in Creative or Survival mode. In Survival, a pickaxe with Efficiency V can help due to being faster (so it's easier to time when to place a new piston and turn).
Minecraft: Java Edition, official Minecraft Launcher. Unmodded, no resource packs or data packs that aren't built-in. Singleplayer world, Creative or Survival mode.
Steps to reproduce
Place a piston on a redstone block, so the piston extends to your left.
Look at the piston at about a 45-degree angle, but slightly to the right.
Quickly replace the piston with a new piston and look left very fast. This can take a few tries to get right.
Observed behavior
If done correctly, the piston will stay facing the same direction and will stay extended. However, a new piston head block will be created, facing a different direction. This new piston head block is a ghost block — right-clicking it will remove it, and so will closing and reopening the world. The new piston head does have collision and does not disappear if it gets updated (for example, if a block is placed next to it). Even trying to break the new piston head does not destroy it or drop an item, but does create block-break particles. Finally, pick-blocking the new piston head does not give an item.
Expected behavior
The old piston and piston head would get removed, and the piston should stay facing the same direction or turn to face another direction. It should then extend (and create a new piston head block).
Attached media
The recordings were made in 1.21.6 Pre-Release 1, but I tested the bug in 1.21.5, and it works there too. I used Windows's built-in Snipping Tool for the recordings and Minecraft's built-in screenshot keybind for the image.
recording.mp4
Video of the bug in Creative mode. This took me a few tries.recording2.mp4
Video of the bug in Survival mode. This took me a few more tries than the first recording. My pickaxe does not lose durability because I gave it the Unbreakable component in agivecommand.image.png
Image of the redstone block, the piston (and the piston head), and the piston head ghost block.
Environment
Windows 11
The Environment field is supposed to only contain PC details.
Thank you for your report!
We are tracking this issue in MC-254385, so this ticket is being resolved and linked as a duplicate.
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