This problem report applies to V14.0.1 on Windows 10.
When I save a file, or “save all”, I occasionally get the error Could not save a backup file. Would you like to continue saving or cancel
To be able to troubleshoot this when it happens, it would be necessary to have as many details as practical as to why the save operation failed, including the full path (including filename) used for the attempted backup.
(I suspect something is broken in the backup code, as usually I can try again later without getting this message.)