Pistons Don't Unextend Unless They Receive A Block Update

I don't know why this happened, it was supposed to make all pistons unextend.

Instead two of them did not unextend.

Steps:
1. Make sure you have minecraft installed.
2. Build the thing that I made in the attachment.
3. Turn it on then off.
4. You should see that two of the pistons will not unextend.