i'm currently trying to create a vault like door where the blocks pull away to let you through then close after a couple of seconds but for some reason one of my sticky mechanical pistons refuse to pull blocks back or pull back at all yet my other two work perfectly

ok, i'm a massive idiot, i forgot to make space for it to pull back so it was trying to pull but due to their being blocks in the way it wouldn't

massive tip, always make sure you clear the space before actually testing it