I was playing on a 1.14.3 Minecraft world with standard generation which I set the world border to 1000. When i came to the border i tried pushing a block of cobblestone outside the world border. The top of the piston gltiched into the cobblestone block, and when i tried removing the piston the block stayed there but without collision. After relogging the block dissapeared but the collision of the block was there.