My Update Manager does not get past showing available updates. After startup, its window is shown in the Gnome Shell overview. I click "install", then authenticate > notification dialogue: "this update involves unauthenticated packages" (or similar, my system is in German), which I ok, because I trust the repos I have enabled. Then update manager is just gone, nothing happens. The next reboot, same procedure, no updates were installed. Here's my /etc/apt/sources.list and apt-get update log I should note that updating via Synaptic or command line works normally, it's just the Update Manager that is broken and that I'd like to fix for next time.