Red - Visual Bug
Green - Real Block
Blue - Drop State

The piston duplicates block in glitch state. Produces a block that looks like it is there though does not drop anything.

1. Pulser Pushes Piston at fast pace.
2. Place a block where player is looking in Picture 1. (Does not always dupe on first place)
3. When the block is on the piston pushes back and forth place a block in the same spot.
4. If you did this correctly is should have created another copy of the block. (TIP: When you place the other blocks to do it again these blocks in your inventory do not actually get used.

EDIT: Any other interactions with the fake block (Break, Piston, Explosion) will make this block disappear.

Piston will only make the fake block disappear if the piston is directly used with the fake block. Using another block to push the fake block will not make it disappear.