I have the same problem. Nowadays initial SSH connection is established but after some packet transmission it's dropped. I believe they have started to drop SSH packets after a limit is reached. I have switched to MOSH https://mosh.mit.edu/. It authenticates using SSH and then switches to UDP. It's faster than SSH and easy to install and use.
To use it, just install it on your server, open udp port 60000:61000 in firewall and connect to the server with a mosh client like you do with a ssh client (There is no need to start anything).
sudo yum install mosh
sudo iptables -I INPUT 1 -p udp --dport 60000:61000 -j ACCEPT
A good windows client is MobaXTerm http://mobaxterm.mobatek.net/download-home-edition.html