SSH connexion disconnects when a progress bar is live on the remoter host

Question

Using, e.g. the following command:

rsync -P -e 'ssh -p 19022' file user@localhost:Downloads/

I'm disconnected from the remote host right afer a few seconds. I'm rarely disconnected from the host, but when a progress bar is live or when something is going on, I'm suddently disconnected. I have to use, e.g. tmux to get back to visualising the progress bar.

It also happens with the following command: watch -n 2 'netstat -patun|grep sshd'

In other words, during a live process, I'm disconnected after a few secs only.

Picture below:

1. I connect to the remote host.
2. I run tmux on the remote host.
3. From the host/tmux, I send a file back to my local machine using rsync.
4. Disconnect happens after a few secs.
5. I input tmux attach to get back into the tmux session.

Basically, any command that I run on the host, that outputs an event currently in progress, triggers a disconnection from the remote. If this command is not run under something like tmux, it is aborted.