Moving your project folders to the new location will take them out of OneDrive control, they should be safe.
Check-in Changes saves an online backup of them anyway
The problem project, if you move it somewhere to temporarily hold it, it takes any possible corrupted files with it, ie hopefully the problem object.
If it all works out, afterwards you can delete this folder
In the rare event it all goes wrong, you can move the folder into the new location
When you log into UEFN it will show a download icon on any maps you have that aren’t on your PC.
Not finding your problem project, it will download the project how it was on your last Check In into a newly created folder.
If you’ve published this island already, your public island code will never change.
But every time you do a memory test or make a private upload it generates a new private map code, the currently active map, will have its own private map code, but be known to the public by your main island code.
No it won’t change the map code that the public will see