When I insert or remove a USB stick, the desktop disappears and I am presented with the login screen. Also happens with SD cards. I login, and the USB stick is mounted. When I eject it from “Files” the same thing happens; the desktop disappears and is replaced with the login screen.
My Librem 13v2 is running a fresh install of the latest PureOS ISO (20180120). I did not have this problem with the PureOS version that was pre-installed when my Librem 13 was shipped.