Ssh connection freezes, how to identify the cause?

Question

linux

Greetings!
Recently, the ssh connection to the server began to freeze after a short break between command inputs. When you try to enter, the cursor just blinks, after a while it dies off and you can enter as usual.
There is almost no load on the processor and the network.
What can be and where to look?

Answer 1

Enable debug on the server and see the log