we encountered a wired issue, for a painful time. The windows 2008 machine A, set up as FTP server using OpenSSH. There is one folder on this FTP server, which is actually share folder on another windows Machine B.
Windows team then enabled all permissions almost everywhere, myself (users/everybody group) can read/write into the share folder directly from any machine. The FTP account can SCP/PSCP any file to the share folder onto Machine A. Wired thing is, the FTP account, if connect through SFTP, it can only read/delete/update files into that share folder, but never able to write new files.
the exception encountered, when uploading file is
sftp> put test.txt test4 Uploading test.txt to //xx/dfs/xx/xx/xx/xx/xx/test.txt Couldn't get handle: Permission denied
Then finally windows team found above link,
and enabled both below Share and NTFS permission.