When a dispenser picks up a block of powder snow while it is moved, a client-side ghost block is created.

To reproduce

1. Build this contraption
   
2. Power the lever
3. Put a powder snow bucket in the dispenser
4. Unpower the lever
   → The block of powder snow is placed and pushed
5. Power the lever again
   → The block of powder snow is picked up by the dispenser, but does not disappear (however breaking particles are created), and is moved by the piston
6. Pick up the powder snow with an empty bucket and try to place it down again
   → Wait it's all air? Always has been

Videos

• https://twitter.com/VoHakon/status/1357246924525613057
• https://www.youtube.com/watch?v=JTHEgWsckbo
• Minecraft 21w05b - Singleplayer 2021-02-10 12-36-30.mp4