Ok, found that info in your logfiles:
As referenced in the FAQ https://central.owncloud.org/t/updates-between-multiple-major-versions-are-unsupported/815 within your github post this is an unsupported upgrade as you have skipped one major version (8.1.x). A correct done upgrade would be:
8.0.3 -> 8.0.14 -> 8.1.9 -> 8.2.7
by following the steps provided in the FAQ above. The important part is that you delete all files and folders except /data/ and /config/ before extracting the new files of the next version you want to jump to.
Further reading is also available in the official documentation:
https://doc.owncloud.org/server/9.1/admin_manual/maintenance/upgrade.html