Comment 19 for bug 1733557

> It depends on the hardware/graphics.

Sure, no. I tested and have this issue on home PC (16.04.3 after latest Unity update, AMD Phenom CPU/Nvidia GPU), work PC (17.10, Intel i7/Intel), Lenovo flex laptop (17.10, intel i5), and of course in VirtualBox (16.04.3 fresh install with latest updates, 18.04).

> But as I said, I can't reproduce it on bionic (bionic has different unity/lightdm version). Can you reproduce it in a live iso?

Not tried live iso, but I have test box with up-to-date 18.04. Just two days ago I tried:

Added second user account;
sudo apt install unity-session lightdm
sudo apt purge ubuntu-session gnome-shell gdm3

Reboot, login as first user, start second user session, end session, return to first user session, lock screen - issue here.

Bionic live iso does not have unity and lightdm preinstalled, so them will be downloaded from repository anyway.