Block 36 (Piston_Extention) Bug

I was playing around with Block 36. I created a new Block from a command block with the command "/setblock 300 62 300 minecraft:piston_extention". I removed the block by clicking on it. After a few times the hitbox of the block got weird. I closed Minecraft and started it again and every thing was normal again. But after I repeated the steps the bug happend again.