Setup:

A portal underground spawns Zombified Piglins.

They are attracted to a nearby turtle egg.

To get to the turtle egg, they walk through a soul sand bubble column which takes them to the surface.

Once on the surface, they keep trying to move to the underground turtle egg, although they cannot reach it.

The Zombified Piglins never break focus on the underground turtle egg, unless reloaded (Quit game, then rejoin).

Once reloaded, they begin to pathfind normally and forget about the underground turtle egg. This indicates that their behavior is a bug.