We've recently been making some security minded changes at work, one of which is ssh-ing though a bastion host/jumpbox, and me, being one of those linuxy types, had some hassles with my ssh working. I was getting errors where both sides of the connection claimed that other one had closed the connection, and some mumbles about pre-auth.
After a lot of time wasted googling, and trying things like limiting the ciphers used, dropping to a 2048 bit key instead of a 4096 one, trying keys without passphrases, I managed to stumble on the ten characters which fixed my connection, and allowed me to ssh with a snippet in ~/.ssh/config via a bastion host
Yup, I forgot the number one rule of computering, which is stop trying to find the most elaborate, complex solution, and start with the easy steps.
It might be annoying, but this is why computer people ask if you've restarted/reloaded things ;-)