When using a Create Dynamic Material Instance node the Get Material node will plug into the World Context Object rather than the Parent input. This will cause a error to be thrown that does not allow the map to be saved with the following warning.
"Can't Save .... Graph is linked to external private object ...."
1. Open UE4
2. Create a BP Actor
3. Add a Static Mesh Component and assign any static mesh
4. Recreate the graph as shown in the attached image
a. For the Get Material > Pull off and search Create Dynamic Material Instance, and choose the second one.
b. On the Return Value just promote to a Variable.
c. On the Create Material node, for the Parent make sure to set any material.
7. Save and Compile the BP
8. Place BP asset in the level
9. Save the map
Results: There will be an error that the map cannot be saved
Expected: The map should be saved.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-24690 in the post.