After some more observation and reading around I tried to deactivate IPv6. Even with IPv6 disabled, the graphical update-manager regularly fails to download the packages. Doing this from the terminal works fine on every attempt.
Have no more ideas as to what to try or adjust -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1412560 Title: Graphical update fails To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/update-manager/+bug/1412560/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
