Ghost sphere appears in scene but not in the world outliner

Development Rendering
1

Hello,

Every time I’m in play mode a mystery sphere using the world grid material appears at a random position. It can’t be found in the world outliner.

Since the actor/mesh can’t be found I’ve tried modding the world grid material to make it completely transparent, but when I click save Unreal crashes (apparently this is a known bug).

Using 4.22.

Any ideas?

Thanks!