Thank you for investigating.
Oh, I don’t know where that is (Developer->Visualize->Mesh Distance Fields).
But I think I know how to reproduce.
When some static meshes are placed on landscape, that will occur.
Skeletal meshes are OK. It seems only static mesh.
I also tested in default sky.
Could you take a look and I hope it helps to investigate.
In (placing my asset)
In (placing unreal asset)
In default sky (placing unreal asset)