ssh diagnostics
Debugging sshd
Run SSH daemon on another port as a part of the command (then you don't need to lost your existing sessions, this tips is useful specially if only have access to the host thought ssh)
sudo /usr/sbin/sshd -d -p 2200
# use -dd instead of -d if you need more logs
# use -dd instead of -d if you need all logs (really very verbose)
Warn: You should run this for each ssh connection.
If you use a personal firewall don't forget to allow connection on port 2200. Or just disable firewall for your tests.