I've been running the Owncloud 9.x series for quite some time. I've only used the official Owncloud repository as a source.
I upgraded last week to a version (I don't recall which one, but it was very incremental and I had no issues), then again today to 220.127.116.11.
After running the upgrade today, I am left with an unusable installation where the main page reads "Downgrading is not supported and is likely to cause unpredictable issues (from 18.104.22.168 to 22.214.171.124)".
My upgrade procedure today was:
$ apt-get update $ apt-get upgrade $ cd /var/www/owncloud $ sudo -u www-data php occ upgrade --dry-run $ sudo -u www-data php occ upgrade $ sudo -u www-data php occ maintenance:mode --off
Operating system: Ubuntu 14.04 LTS
Web server: 2.4.7-1ubuntu4.13
PHP version: 5.5.9+dfsg-1ubuntu4.20
ownCloud version 126.96.36.199
Updated from an older ownCloud or fresh install: Updated from older ownCloud
Special configuration (external storage, external authentication, reverse proxy, server-side-encryption): No special configuration