So the only other suggestion that I know of that could resolve the Externally Referenced issue which was mentioned as the last comment on the post I linked.
“Try deleting your ‘Saved’ folder in your project files. This worked for me after the rename trick failed, likely because I copied my whole project from another computer, and then upgraded to a newer version.”
Hopefully that can do the trick, but let me know if you are still in need of assistance.
Cheers,