I am on a Dell Precision 5520 running 18.10 with default settings, nvidia drivers, and updated this morning. The bug started yesterday or the day before.
I have the laptop set to suspend on lid close. Since yesterday, when I open the lid and the display comes back on, the lock screen doesn't display. I see the dock bar on the left, the menu at the top, and either all black or whatever I was working on in the middle. I can move the mouse, but cannot interact with anything in the dock or the main display. I CAN interact with the power dropdown at the top right, where I can select a "pause" logo- which will cause the power to go off (fully suspending the machine presumably)... and from there when I wake it back up, the lock screen is properly displayed. I have ALSO tried mashing function keys to restart the GUI, and a couple times some combination of alt-ctrl-shift and some function keys have gotten me to a working login screen (and after typing my password, back to my working session) but it hasn't worked that way when trying to do it scientifically and press the buttons slowly to figure out which ones caused it.
ProblemType: Bug
DistroRelease: Ubuntu 18.10
Package: gnome-shell 3.30.1-2ubuntu1
ProcVersionSignature: Ubuntu 4.18.0-10.11-generic 4.18.12
Uname: Linux 4.18.0-10-generic x86_64
NonfreeKernelModules: nvidia_modeset nvidia
ApportVersion: 2.20.10-0ubuntu13
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Tue Oct 23 19:37:49 2018
DisplayManager: gdm3
InstallationDate: Installed on 2018-05-15 (161 days ago)
InstallationMedia: Ubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180426)
ProcEnviron:
TERM=xterm-256color
PATH=(custom, no user)
XDG_RUNTIME_DIR=<set>
LANG=en_US.UTF-8
SHELL=/bin/bash
SourcePackage: gnome-shell
UpgradeStatus: Upgraded to cosmic on 2018-10-11 (12 days ago)
Please run these commands and send us the resulting files:
lspci -k > lspci.txt
dpkg -l > dpkgl.txt