Pistons are not retracting

When activating pistons, they do push, but upon deactivation they don't retract.

I thought the sticky piston would retract and pull the block in like they normally do.

It did not retract until the block that was stuck to the piston head was removed. This happened with all types of blocks I tried (Iron, Wooden Planks, Cobblestone, and Dirt). The same happened with regular pistons.

I put a piston up to a block, activated it with a lever, redstone torch, or what-have-you, and the piston pushed the block. I destroyed the lever/redstone torch, but it did not retract. When I broke the block it had pushed, it then retracted to it's OFF state.