(1) So it looks like
ssh disconnects unexpectedly. Using ssh -v (or ssh -vv) may give us some clue. Can you run sshd -d (possibly on a different port, so the regular sshd is not affected) in the destination, replicate the problem when connecting to it and show us what it says? (2) About how long does sending 78 MB take? Put pv -qL … between tar and ssh and limit the transfer rate, experiment. The point is to tell if your ssh tends to disconnect after a certain time or after some amount of data maybe. // [Edit] the question and add the results.