Comment 1 for bug 1573653

Roman, only N->(N+1) upgrades are supported - you can't skip Kilo: you should do Juno->Kilo, then Kilo->Liberty upgrade instead.

Based on the discussion in https://bugs.launchpad.net/nova/+bug/1511466 my understanding is that the reporter forgot to force data migration of remaining instances (db sync only migrates DB schema and does not touch DB rows for availability sake).