At some point the way that chest shop signs worked was modified. If a sign is above and in front of a chest, it now applies to the chest it is in front of instead of the chest it is on top of.Unfortunately this breaks multiple shops including mine. (I know of fairshop and sgt_pepper4 should also be affected and there are likely dozens more.) Nobody can buy from the bottom chest except using signs in front of them.I'm not sure if the change was deliberate. This is the first I've heard of it.