When I push a slime block with a piston, and launch myself into the air, and the piston retracts after the length of time a button is depressed, occasionally (not always) the slime block and piston combo remains pushed in the air by the piston. The is only graphical, you can walk through the slime block and when you update the piston, it instantly removes the glitch.

EDIT: Sometimes the button appears depressed forever, and the redstone is constantly on. Sometimes the slime block disappears entirely.

Steps to Reproduce:
1. Put a piston facing up on the ground.
2. Wire it up to a stone button.
3. Put a slime block surrounded by obsidian on top of that.
4. Launch your self into the air repeatedly, one of the times it should create the glitch.