Yes, it broke everything to where we get "502 bad gateway" on every site.
We see two important errors:
WARNING!
Some problems are found during reinstall chained SSL certificates(see log file: /var/log/plesk/install/plesk_12.0.18_repair.log)
and
Try to restore database from /var/lib/psa/dumps/mysql.preupgrade.12.0.18-12.0.18.20140926-001226.dump.gz manually