I have seen this in many versions, but here is the bug: So, I was using a torch/redstonedust monostable, which gives a 1 tick off pulse. And then I have a piston with more than 1 block of sand. Basically, I am trying to not use sticky pistons in my build, so I use sand: and this is what happens (look at screenshots). In other words, every time the piston quickly retracts and then extends again, 1 sand dissapears. It's actually pretty annoying!