I mean, give the shutdown command like this, not after already choosing it via menu. This way you may catch what's wrong. Also, you can check the logs when you boot next time via journalctl -b -1 but to make it easier maybe this one should be more helpful journalctl -b -1 | grep -i shutdown

(They meant, instead of doing your normal shutdown, open a command window and type that command instead.)

I was also experiencing your same issue, just tried @muhyb@programming.dev's recommendation, and my computer shut off completely as desired.

Edit: I also opened a terminal and "sudo poweroff" and "sudo shutdown now" both work, so for me, I didn't need to switch to a TTY console.