What is the SFTP server? In that version there were three supported options: OpenSSH, Cygwin (OpenSSH), or TitanFTP.
What do the SFTP server logs show? Are any of the commands issued by DRS (eg list directory contents, read file) denied? Are you able to access the SFTP server from a client such as WinSCP and view/download the files?
PS- You could just export the VM using the VMware client and then export it to the new host. That would be a lot simpler, although it is worth knowing that DRS will work if you actually need it.