Struct does not appear to save changes after compiling and saving it resets to null

When making a change to a struct that is used in a blueprint some assets do not appear to save changes.

Additional notes: Using the Reload option (Right click struct > Assets actions > Reload) appears to resolve this issue.

1. Download the attached project
2. Open the project
3. Open "BP_Gamemode"
4. Open Class Defaults
5. In the details panel Set Title Material to "M_Logo_UI" (Class defaults > Details panel > Fallback Theme > Title Material)
6. Compile and Save
7. Click the drop down for "Fallback Theme"

Result: The Title Material will be reset to null/ none
Expected: The change would be saved