That's just saying that things are tripping each other up whilst trying to shutdown.

Try sudo journalctl -b-1 --reverse

That will show the last system log in reverse order, and might help see what's going on.

There's an old bug report (notice I say report, as it's locked and not solved - & I don't have the link to hand) with several people saying that systemd causes this, but, it might be applications or services that have user accounts open, etc, etc...

but... try shutting down services and unmounting any shares / filesystems that might be causing this to see if you can isolate something.

As mentioned in the other thread, try shutting down from the command line on a new TTY (text-only screen) and see if that shows anything else.