Since this week: unable to do "git pull/push/clone..." from console

After a couple of years working, since this Monday when I use a console command like “git pull” in my Ubuntu Linux I have successful auth but then get a fail processing the command:

... successful auth logs here ...
debug1: Sending command: git-upload-pack 'myuser/myrepo.git'
debug2: channel 0: request exec confirm 1
debug2: callback done
debug2: channel 0: open confirm rwindow 0 rmax 32768
Write failed: Broken pipe
fatal: Could not read from remote repository.
Please make sure you have the correct access rights
and the repository exists.

But my WebStorm/Idea IDE works fine via UI! So I suppose this is a trouble of incompatibility with my console SSH client. The version of my SSH client is:

OpenSSH_6.6.1p1 Ubuntu-2ubuntu2.13, OpenSSL 1.0.1f 6 Jan 2014

Docs of GitLab say that OpenSSH versions >= 6.5 are supported.
So I do not understand why it stopped working for me.
Any idea?

I’ve discovered that adding this line to /etc/ssh/ssh_config fixes this issue for some other servers which became having the same issue:

IPQoS throughput

Does anybody know what happened on my side?
Unfortunately this does not fix GitLab SSH, but both the issues raised at one time, so I think they are related.

Adding these both lines to ssh_config helped:

IPQoS throughput
ProxyCommand nc %h %p

No idea why.