I was doing some experimentation with the sticky pistons and redstone blocks. I noticed that you can make sticky pistons push a redstone block, and pull it back, when it's facing the sides and the bottom, but it won't do the same for the top. It gets stuck after turning off the power source that's pushing the piston.

When I remove the redstone block, the piston then retracts back. Hope I explained the issue well enough!

EDIT: I will post pictures if issue needs to be explained more.