This is likely to have been caused by bug 556132, which is now fixed. Searching google for "ssh rekey hour" finds plenty of FAQs about various SSH clients (e.g. SSH Corp's client) that automatically initiate a rekey after exactly one hour by default, perhaps current OpenSSH does too, and that would have provoked this problem. So perhaps we should close this bug.
This is likely to have been caused by bug 556132, which is now fixed. Searching google for "ssh rekey hour" finds plenty of FAQs about various SSH clients (e.g. SSH Corp's client) that automatically initiate a rekey after exactly one hour by default, perhaps current OpenSSH does too, and that would have provoked this problem. So perhaps we should close this bug.