I cannot save my map

Hello everyone,

I’ve searched online and I’ve seen others have similar problems but in past versions of the Unreal Engine. I’ve read that its a bug that got fixed and other sources provide somewhat confusing fixes for the issue in previous builds of Unreal.

The Problem
Everything is fine and I can save my world up until I place a single blueprint/object into my scene.
Here is the blueprint for the object. Nothing is in the event graph. Its all in the construction graph.

It then says this when I try to save. "Can’t save …/…/…/…/NewProjectCombat/Content/ThirdPersonBP/Maps/ThirdPersonExampleMap.umap: Graph is linked to private object(s) in an external package.
External Object(s):

Try to find the chain of references to that object (may take some time)?"

I don’t understand what the issue is. What object(s) are private and how do I make them public? What external package has these objects? It mentions the MaterialInstanceDynamic which I assume is referring to a material, “GhostMeshMaterial” that I made and channeled into a dynamic material instance, “Dynamic Ghost Material”.