Put the summary of the bug you're having here

What I expected to happen was...:
Pistons should retract after the power source is removed

What actually happened was...:
The pistons stay extended

Steps to Reproduce:
1. Place sticky piston facing upwards with redstone block on top
2. Place a redstone block next to the sticky piston to extend it
3. Remove the redstone block to the side
4. Piston stays extended