https://forum.duplicati.com/search?q=unc%20in%3Atitle%20order%3Alatest found
Restore GUI not working correct with UNC source leading to open issue
When restoring a backup with multiple server UNC paths, file browser cannot be navigated until a search is performed. #3722 which s a pretty ugly work around (but because you asked for a work around it may help)
If your problem is similar but different, it might be helpful if you could add your experience with it to the Issue.