If you’ve seen a similar notification, I empathize with your pain. I don’t know that there is one solution to this problem, either, so I’m going to share a number of them we’ve used and hope that one (or all) of them will help you.

Basically a file is added through file explorer (a cloud library in OneDrive or SharePoint being synced locally to your computer) but then after a moment a notification appears which says “You now have two copies of a file; we couldn’t merge the changes in [filename]” and then the filename is appended with your computer name again and again until eventually the filename is too long and is harder to delete. Let’s not get to that point.