Hello, I had the same problem.If you made a backup of your configuration files ;-) , you can view that there is one change in your sshd_config (server side):
# diff -b sshd_config /etc/ssh/sshd_config 73c73 < KeepAlive yes ---
TCPKeepAlive yes
So, one working solution is to modify TCPKeepAlive to KeepAlive and reload your server.
Have a good day. Jeremy