When my XPS 13 9380 is plugged into my WD15 dock, clicking the suspend button just takes me to the lock screen. Then when I enter my password the screen goes black and the system suspends. This issue has not happened to me when I'm not plugged in. I'm using GNOME shell.
There are a few other threads (e.g. this one) describing something similar, but in all of them the issues are caused by the NVIDIA proprietary driver. My laptop only has the Intel integrated UHD 620, so those solutions don't apply. Besides, my laptop does suspend - it just doesn't do it unless I log back in.
sudo pm-suspend? – You'reAGitForNotUsingGit Jun 22 '19 at 23:32