Yes, it was enabled with Code: PermitRootLogin yes , but does not work for me. I have to set extra allow for my ip and work. Second, i had a problem with sending emails via thunderbird, roundcube..., i can recieve mails, but can not sent. In this case i have to allow senders in isp config - type name of email address, after that i can sent emails. Looks like that after upgrade are all request denied, maybe thats good for security? I am not sure, I have never had the same problem. Everything else working fine, apache, db etc...does not work rkhunter with new debian and isp config, but this is not important for me.
I have a guess what the less than one minute intervals are. have you got multiple SSH keys in your ssh-agent? pagent? Each key is an authorisation attempt. I had an issue where I had to many keys in my .ssh directory on ubuntu and got locked out for too many failed attempts. Now I have 0 keys in .ssh. Moved them all into .ssh/keys started using .ssh/config to set up ssh users/hosts. basically using the config to say use this key thats located in the keys directory for this host. I have lots of hosts including git so it prevents any problems. The result. 0 failed keys unless there is a problem with the key. kinda useful.