When in an End City, the shulker box mobs have multiples of themselves in the same block. For instance when walking up to a doorway and a shulker box is mounted on the wall next to it, I hit it with arrows but after I kill it there's another one still there, sometimes there's up to four shulkers in the same spot so I'm going through a million arrows or draining my infinity bow on them. This is occurring on every shulker mob I come across in the end.