When renaming or moving a map with a landscape in it this will fail and an error prompt will appear.
Result: An error prompt appears: Can't save ../../../../../UE4/DeleteME/Content/NewMap2.umap: Graph is linked to private object(s) in an external package. External Object(s): LandscapeMaterialInstanceConstant_2 Try to find the chain of references to that object (may take some time)?
Expected: The level will be renamed or moved successfully.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-62150 in the post.