I build a blaze farm and I used only sticky pistons except for on piston that had to be normal. What was meant to happen is that when the pressure plate is active the piston would be on a clock and push out and pull in until there is nothing on the pressure plate.
However now that a go in to change something I see that the piston was not there so I try to place a new one but it seemed there was something in the way. It seems like the piston has gone invisible but its out line was on the side of a block next to it. I could remove the block but the out line was still there. I can walk through it but cant break it or place something in its place.
I have no idea how to trigger it but solved while uploading the attachments. I placed block from the top and now it gone, but it still shouldn't have happened.