on my Linux Mint 19 "Tara" system with cinnamon desktop, when I shutdown via the GUI, the system halts for 1 min and 30 seconds, and a text says
A stop job is running for Session c2 of user ... (1min 30s)".
I've googled similar problems, unfortunately I'm not fit enough in Linux to find out what is blocking the shutdown here.
When I logout from the GUI first und shutdown then, everything works fine.
Thanks a lot for all usefull hints!