Please help us by providing the following info. Before posting please also check the pinned "Known issues" threads and make sure that you're running the latest available version for your oC release: https://owncloud.org/changelog/
Steps to reproduce
1.set up 2 different servers. Both servers started from before 9.0.x
2. upgrade both servers in the correct order to 9.0.x
3. One server stops auto upgrade at 9.0.5 and other server is at 9.1.5
Expected behaviour
Both servers should be at 9.1.5
Actual behaviour
One server is stuck on 9.0.x
Server configuration
Operating system: Both servers at Ubuntu 14.04.5
Web server: Apache 2.4 (both)
Database: MySql 5.5.55 (both)
PHP version: 5.6.23 (stuck at 9.0.x), 5.5.0 (upgraded to 9.1.x)
ownCloud version (see ownCloud admin page):
Updated from an older ownCloud or fresh install: Upgraded
Special configuration (external storage, external authentication, reverse proxy, server-side-encryption):
ownCloud configuration
ownCloud log (data/owncloud.log)
Integrity status for oC9+
No errors have been found.