Rename of tmp file fails on macOS

[tn63942]

I have the native SFTP server active on my mac mini running macOS High Sierra. A user running FreeFileSync on a Windows 10 box has read/write permissions and all works okay writing a file from his machine to mine until the write is complete and FreeFileSync tries to rename the file from its ".tmp" designation to the actual name. The rename command always fails. Using a completely separate machine using Cyberduck, I connected and tried to rename a file and it fails also. So, I do not suspect FreeFileSync is at fault. However, is there a setting that will let FreeFileSync write files under their correct file name and skip the whole ".tmp first" process?

[Zenju]

Options -> fail-safe file copy

[tn63942]

Many thanks!