when a lot of endermen teleport to the same location, in this case a lot of endermen were tearing down a tower to get an endermite, lots of endermite appear, and that causes them to put their tails really floppy and you can't do anything with them (you can't interact with them)

You can not kill them with lava, and if you break the block they are stuck in, they will get stuck in the block under.