You seem to have installed a version of a package which is not the one from the official Ubuntu archive.
>From your VarLogDistUpgradeAptlog.txt file: Investigating (9) libdvdnav4 [ i386 ] < 5.0.3-1~trusty -> 5.0.3-1 > ( universe/libs ) The official version for trusty is 5.0.3-1. You might try reinstalling the official one and see if that resolves the upgrade for you. ** Changed in: ubuntu-release-upgrader (Ubuntu) Status: New => Invalid -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1750723 Title: Unable to Upgrade to 16.?? To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/ubuntu-release-upgrader/+bug/1750723/+subscriptions -- ubuntu-bugs mailing list firstname.lastname@example.org https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs