With SFTP protocol, when automatic transfer resume is enabled, WinSCP first uploads the file to a temporary file with
.filepart extension. Only after the transfer is completed the file is renamed to its actual name.
For you the renaming failed, for which there are many possible reasons including:
- Your SFTP server does not support renaming files;
- There’s some process that takes the uploaded file away immediately, before WinSCP is able to rename it.
- There’s antivirus (or similar application) that starts inspecting the uploaded file, locking it while doing that, what conflicts with WinSCP attempt to rename the file.
To circumvent that, disable transfer resume/transfer to temporary filename.