How to solve the problem, the error "remote side unexpectedly closed network connection" crashes when working through putty via ssh?

Question

SSH

There is docker ubuntu 18.04.3 LTS (GNU/Linux 4.2.8 armv71). When connected via putty to the ssh server, 10-15 seconds pass and the error "remote side unexpectedly closed network connection" appears.

I look at the server with the sudo ssh status command, ssh is not working (:

The sudo /etc/init.d/ssh restart command helps
After this command, everything seems to be fine:

If the docker is rebooted, the server works, but after the first connection via ssh everything repeats:- (
Output of #journalctl -u ssh , and its last result:
Dec 29 15:32:46 ubuntu-bionic-armhf-1 systemd[1]: Started OpenBSD Secure Shell server.
Dec 29 15:33:17 ubuntu-bionic- armhf-1 systemd[1]: ssh.service: Main process exited, code=killed, status=9/KILL
Dec 29 15:33:17 ubuntu-bionic-armhf-1 systemd[1]: ssh.service: Failed with result 'signal'.
Dec 29 15:33:17 ubuntu-bionic-armhf-1 systemd[1]: ssh.service: Service hold-off time over, scheduling restart.
Dec 29 15:33:17 ubuntu-bionic-armhf-1 systemd[1]: ssh.service: Scheduled restart job, restart counter is at 4.
Dec 29 15:33:17 ubuntu-bionic-armhf-1 systemd[1 ]: Stopped OpenBSD Secure Shell server.
Dec 29 15:33:17 ubuntu-bionic-armhf-1 systemd[1]: Starting OpenBSD Secure Shell server...
Dec 29 15:33:17 ubuntu-bionic-armhf-1 sshd[454]: Server listening on 0.0 .0.0 port 2222.
Dec 29 15:33:17 ubuntu-bionic-armhf-1 sshd[454]: Server listening on :: port 2222.
Dec 29 15:33:17 ubuntu-bionic-armhf-1 systemd[1]: Started OpenBSD Secure Shell server.
Dec 29 15:33:49 ubuntu-bionic-armhf-1 systemd[1]: ssh.service: Main process exited, code=killed, status=9/KILL
Dec 29 15:33:49 ubuntu-bionic-armhf-1 systemd[1]: ssh.service: Failed with result 'signal'.
Dec 29 15:33:49 ubuntu-bionic-armhf-1 systemd[1]: ssh.service: Service hold-off time over, scheduling restart.
Dec 29 15:33:49 ubuntu-bionic-armhf-1 systemd[1]: ssh.service: Scheduled restart job, restart counter is at 5.
Dec 29 15:33:49 ubuntu-bionic-armhf-1 systemd[1 ]: Stopped OpenBSD Secure Shell server.
Dec 29 15:33:49 ubuntu-bionic-armhf-1 systemd[1]: Starting OpenBSD Secure Shell server...
Dec 29 15:33:49 ubuntu-bionic-armhf-1 sshd[456]: Server listening on 0.0.0.0 port 2222.
Dec 29 15:33:49 ubuntu-bionic-armhf-1 sshd[456]: Server listening on :: port 2222.
Dec 29 15:33:49 ubuntu-bionic-armhf-1 systemd[1]: Started OpenBSD Secure Shell serv
On the advice of @pfg21 I tried the following options in /etc/ssh/sshd_config on the server
TCPKeepAlive yes
ClientAliveInterval 60
ClientAliveCountMax 360
does not help....
How to solve this problem so that sshd does not crash and works stably. Thank you!

Answer 1

Solution:
In sshd.service

$sudo nano /etc/systemd/system/sshd.service

you need to set the key in the [Service] section to:
problem solved and don't forget to reload all these wonders:

$sudo systemctl daemon-reload
$sudo /etc/init.d/ssh restart

Answer 2

throw more shutdown intervals
i.e. write the following parameters to /etc/ssh/sshd_config on the server
TCPKeepAlive yes
ClientAliveInterval 60
ClientAliveCountMax 360