The newest Windows 10 update (1809, or October update) has been plagued with teething issues. Most recently, some users have documented one of them on Reddit. This bug results in the failure to bring up dialogs that prevent the loss of data through conflicts or duplication during transfer.
https://www.notebookcheck.net/Windows-has-another-new-October-update-issue-to-fix.341331.0.html
I discovered this bug about day after updating to 1809 build. I sent report by feedback center, so far without response. It is hard to keep track of the feedback because of yet another bug in feedback center that keeps telling you that it cannot connect to the Internet unless you logout and login back.