Put the summary of the bug you're having here
What I expected to happen was...:
When i put a sticky piston on top of another sticky piston i expected it to stick to that sticky piston
What actually happened was...:
It did stick to the other sticky piston but it did fail to stick after it had contracted a few times
Steps to Reproduce:
1. Place a sticky piston facing upwards
2. place another sticky piston on top of that
3. wire it up with redstone
4. Then the sticky piston dosent 'stick'
Is the piston that you're trying to pull powered?...