I had a automatic pumpkin harvester, and when i smashed the pumpkins in a previous version it would go down and water would swoop across. Also I had a sugar cane farm. What happens when I try to double push the pistons (one piston on top of one another and 2 stack of sugar cane in front and both pistons are activated by a torch and a repeater with the torch activating the repeater which activated the 2 pistons) the top piston would push and the top piston would stay out. Thats not all it duplicates the push block entity. Then it would have one sticking out and one not. As if it was double activated. I believe its because your breaking the bottom block before the top and making it glitch. When I put regular blocks in front of the pistons it works just fine.
Back to the malfunctioning piston pushing items, it gets stuck in them and likes to be pushed off to the side as if there was a outwardly force.