Reflection FTP Client Error - Message length read returned 0. Assume Connection closed

I have a client who uses some form of the Reflection FTP client, and I have very little experience with this solution. We recently upgraded our SFTP/SSH server and 90% of our clients have been able to continue connecting as normal, but this one client who uses this Solution has been unable to complete a successful connection. FYI our (very) old ftp server was running this version of SSH:

$ ssh -v localhost
OpenSSH_3.9p1, OpenSSL 0.9.7a Feb 19 2003

Our new server, a SuSE based server is running a slightly newer version:

$ ssh -v localhost
OpenSSH_6.6.1, OpenSSL 1.0.1i-fips 6 Aug 2014

Here is the issue as I see it: They are able to initiate a connection, getting through our firewall whitelist and able to successfully log in using the same credentials they always have. In our SFTP Logs I can see a successful connection and that our system accepts the password.

Here is a sample of our own log file:

2017-02-10T10:26 sshd[26695]: Accepted password for USER from IP port PORT ssh2
2017-02-10T10:26 systemd[1]: Starting Session 3903 of user USER .
2017-02-10T10:26 systemd-logind[726]: New session 3903 of user USER.
2017-02-10T10:26 systemd[1]: Started Session 3903 of user USER.
2017-02-10T10:26 systemd[1]: Started User Manager for UID UIDNO.
2017-02-10T10:26 systemd-logind[726]: Removed session 3903.

Not very useful on my end. Basically, immediately after a successful log in their system disconnects them. After talking with the client they supplied a log file from their Reflection system:

Reflection FTP Client (version: 14.1.70) logging started
02/13/2017 12:25:41 SFTP MYSITE.COM USER
02/13/2017 12:25:44 error: Message length read returned 0. Assume Connection closed
02/13/2017 12:25:44 Connection closed to MYSITE.COM
02/13/2017 12:25:44 A Secure Shell error occurred while trying to make a connection.
02/13/2017 12:25:44 (7) Connection lost.
02/13/2017 12:26:29 dir
02/13/2017 12:26:29 A connection has not been established

This log file was a little more informative, with some sort of error message, in this case Message length read returned 0. Assume Connection closed

Finally, I was able to get them to send me a more verbose log which I will paste at the very end. Long story short this file seems to report the same error as above. Has anyone dealt with a similar issue with this Reflection software, or care to make a suggestion as to our own server settings?

Apparently stack overflow won't let me past the entire 150+ lines of the log file. Attempting to remove everything before the successful login.

Reflection FTP Client (version: 14.1.70) diagnostic logging started
02/13/2017 12:33:46 Loading site properties: COMPANY
02/13/2017 12:33:46 SFTP MYSITE.COM USER
02/13/2017 12:33:52 debug1: Authentication succeeded (password).
02/13/2017 12:33:52 debug1: Login completed
02/13/2017 12:33:52 debug1: Cleanup PKI subsystem
02/13/2017 12:33:52 debug1: PKI_DestroySession called. Session id: SESSION_ID
02/13/2017 12:33:52 debug1: PKI_Cleanup called. Reference count: 1
02/13/2017 12:33:52 debug3: SSH connection thread connect event occured.
02/13/2017 12:33:52 debug3: ssh_session2_open: channel_new: 0
02/13/2017 12:33:52 debug2: ssh_session2_setup: id 0
02/13/2017 12:33:52 debug1: Sending subsystem: sftp
02/13/2017 12:33:52 debug1: channel 0: request subsystem
02/13/2017 12:33:52 debug1: channel 0: open confirm rwindow 0 rmax 32768
02/13/2017 12:33:52 debug3: Application connection thread signaled connect event.
02/13/2017 12:33:52 debug3: Waiting for sftp subsystem to get setup...
02/13/2017 12:33:52 debug1: Request for subsystem 'sftp' succeeded on channel 0
02/13/2017 12:33:52 debug1: Channel 0 request: exit-status 255
02/13/2017 12:33:52 debug3: Callback set application exit status (255), (255)
02/13/2017 12:33:52 debug1: channel 0: rcvd eof
02/13/2017 12:33:52 debug1: channel 0: output open -> drain
02/13/2017 12:33:52 debug1: channel 0: obuf empty
02/13/2017 12:33:52 debug1: channel 0: close_write
02/13/2017 12:33:52 debug1: channel 0: output drain -> closed
02/13/2017 12:33:52 debug1: channel 0: rcvd close
02/13/2017 12:33:52 debug1: channel 0: close_read
02/13/2017 12:33:52 debug1: channel 0: input open -> closed
02/13/2017 12:33:52 debug1: channel 0: almost dead
02/13/2017 12:33:52 debug1: channel 0: gc: notify user
02/13/2017 12:33:52 error: Message length read returned 0. Assume Connection closed
02/13/2017 12:33:52 debug3: Application connection thread disconnect event signaled.
02/13/2017 12:33:52 debug1: channel 0: garbage collecting
02/13/2017 12:33:52 debug1: channel_free: channel 0: client-session, nchannels 1
02/13/2017 12:33:52 debug3: channel_free: status: The following connections are open (1 channels):
02/13/2017 12:33:52 #0 client-session (t:4 r:0 in:3/0 out:3/0 fd:-1/-1)
02/13/2017 12:33:52 debug3: channel_close_fds: channel 0: r -1 w -1 e 5
02/13/2017 12:33:52 debug3: g_iNumberChannels remaining = 0
02/13/2017 12:33:52 debug1: Exiting Client Work Loop. Exit Status 255
02/13/2017 12:33:52 debug1: Transferred: stdin 0, stdout 0, stderr 0 bytes in 0.0 seconds
02/13/2017 12:33:52 Connection closed to MYSITE.COM
02/13/2017 12:33:52 debug3: Destroying COM connection service.
02/13/2017 12:33:52 A Secure Shell error occurred while trying to make a connection.
02/13/2017 12:33:52 (7) Connection lost.