man 5 ssh_config
TCPKeepAlive Specifies whether the system should send TCP keepalive messages to the other side. If they are sent, death of the connection or crash of one of the machines will be properly noticed. This option only uses TCP keepalives (as opposed to using ssh level keepalives), so takes a long time to notice when the connection dies. As such, you probably want the ServerAliveInterval option as well. How‐ ever, this means that connections will die if the route is down temporarily, and some people find it annoying.
echo TCPKeepAlive true >> ~/.ssh/config could prevent those dead ssh-sessions after resume. Let’s give it a try.