Sticky piston glitch involving pulling blocks

While trying to make a trap floor I discovered a bug. Not sure if it's been reported yet or not but I have 4 pistons setup. Two pistons pull the other two pistons after a delay. The first set of pistons are supposed to retract with a block, which they do, and then the other set of pistons are supposed to pull back the first set of pistons. This all works except for the fact that the first set of pistons don't bring the block along with them after being pulled back by the second set of pistons. I have taken pictures to show you. The first picture is my setup (WARNING! BIG PHOTOS) http://puu.sh/1URWI and this is what happens when I press the button http://puu.sh/1URXQ .