I'm having a similar issue here with "AppStream cache update completed, but some metadata was ignored due to errors." following the use of sudo apt update && sudo apt full-upgrade.
sudo apt policy fwupd fwupd: Installed: 0.7.0-0ubuntu4.3 Candidate: 0.7.0-0ubuntu4.3 Version table: *** 0.7.0-0ubuntu4.3 500 500 http://us.archive.ubuntu.com/ubuntu xenial-updates/main amd64 Packages 100 /var/lib/dpkg/status 0.7.0-0ubuntu4 500 500 http://us.archive.ubuntu.com/ubuntu xenial/main amd64 Packages -- You received this bug notification because you are a member of Ubuntu Desktop Bugs, which is subscribed to appstream in Ubuntu. https://bugs.launchpad.net/bugs/1575248 Title: "AppStream cache update completed, but some metadata was ignored due to errors." on "sudo apt-get update" To manage notifications about this bug go to: https://bugs.launchpad.net/appstream/+bug/1575248/+subscriptions -- desktop-bugs mailing list desktop-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/desktop-bugs