This bug has been added to the tracker:
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Bug reports without an attached log file are usually useless.
I have a similar problem where I upload a .zip file using the .NET to an OpenSSH SFTP site on the same windows machine.
Its presence isn't recognized by winscp - as either part of a directory listing or a FileExists() call.
The WINSCP shell doesn't recognize it either.
Script:prefix should be what WinSCP prints on the console.
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