To the point here, If a piston is placed to push up, with a redstone block on top, when the piston is pushed up, it cannot go down, unless removed/redstone block removed. i have a screenshot of the stages.
MC-17182
Redstone Block/Piston Bug
Resolved
Duplicate
0
Name Here
(Unassigned)
Unconfirmed
Minecraft 1.5.1, Minecraft 1.5.2
Retrieved
180th Duplicate of MC-108, please use the search function to see if your bug has already been submitted. Currently over 57% of tickets are being closed as duplicate.