SFTP failure from unix to windows server

Hi,

I am having unix server SUNW,Sun-Fire-V245.
remote windows server details: Microsoft Windows [Version 5.2.3790]

In my script i am sftp'ing files to the windows server through sftp command.

But the problem i am facing is, some files are successfully sftp'd to windows server and for some files sftp is getting failed.

Not sure what is the error and not sure what is exact issue.

i am maintaining the log for sftp'd files. But this log file is also having no information for the sftp failured files.

Could you please guide what could be the exact reason.

Thanks in Advance.