Please connect to the SFTP server and provide the following lines from the session status window.
Code:
Key exchange: diffie-hellman-group-exchange-sha1. Session encryption: aes256-ctr, MAC: hmac-sha1, compression: none.
Connection established with OpenSSH_4.3 (SFTP v3)
This will show us which KEX, CIPHER, and MAC algorithms you're using and whether or not you have compression enabled, plus the SFTP server brand and version you're connecting to.