I have noticed that either 127.0.0.1 is deleted from
server_localhost.alias.drushrc.php or server IP from
server_master.alias.drushrc.php on upgrade, or even when added again manually in the table, on every server verify task.
It is because
function hosting_ip_save() calls
hosting_ip_delete_revision(), and since there is no longer revision there, and
vid has been replaced with
nid in the
function hosting_ip_delete_revision, it effectively deletes the record from the
hosting_ip_addresses table, which causes missing IPs and all the mess which follows, when there are IPs used/expected in vhosts and not just wildcards.