a phenomenon that disappears randomly when he is brought to Overworld by a piston.

Sending shulker from The End to Overworld several times, but he keeps disappearing without settling down in Overworld.

It's the same with the latest version. The problem with this is that when you send five or so of them on the ending portal separately, only two or three of them settle down in the Overworld, and the other few disappear. I don't think the map itself is an error, but it keeps happening in the latest version.

(Note that it's a problem that sometimes happens when you push him down to the piston. It also happens when I make a new map.