Redstone And Piston Bug

What I expected to happen was...:
When i fliped a lever a piston should close

What actually happened was...:
Instead, 8of the pistons closed but 2 got stuck

Steps to Reproduce:
1. Create something like this: http://imgur.com/a/tTJKc
2. Flip lever once
3. Everything closes
4. Flip again
5.There ya go, stuck piston