This is more of a comment than an actual issue with your current packages. I have been updating my packages to the most recent versions, and when I update to gnome-session-ubuntu to 3.23.4.1 (the most recent package version both on git.gnome.org and launchpad.net), I get a 90 second stop job delay on shutdown. As soon as I downgrade to 3.22.2 (your current testing version), the problem disappears. Figured a heads-up to you might be a nice thing.
This is more of a comment than an actual issue with your current packages. I have been updating my packages to the most recent versions, and when I update to gnome-session-ubuntu to 3.23.4.1 (the most recent package version both on git.gnome.org and launchpad.net), I get a 90 second stop job delay on shutdown. As soon as I downgrade to 3.22.2 (your current testing version), the problem disappears. Figured a heads-up to you might be a nice thing.