When a sticky piston is retracting with a certain block, an entity on top of/inside of that block can be pulled through blocks, and into the ground. Players and entities can also completely fall through the ground if there is sufficient space beneath. This is easier of the player or entity is in motion.

Blocks affected by this glitch include:

• Fences
• Brewing Stand
• Iron Bars

It is worth noting that there may be more blocks similar to these ones that are also affected.

How to reproduce:

1. Create a contraption similar to the one shown in the attached video.
2. Place one of the affected blocks on top of the sticky piston.
3. With an entity standing on top of the block, activate the piston on and off repeatedly and observe its affects.