I'm not sure what the conditions are for that screen showing or failing to show (usually the latter in my experience), but your journal.txt says:
Dec 08 09:46:19 robot gnome-shell[1637760]: Error in freeze/thaw accounting
Dec 08 09:46:19 robot gnome-shell[1637760]: GNOME Shell crashed with signal 5
Dec 08 09:46:19 robot gnome-shell[1637760]: == Stack trace for context 0x55d585a44220 ==
Dec 08 09:46:19 robot gnome-shell[1637760]: #0 55d585f7f1d8 i resource:///org/gnome/shell/ui/windowManager.js:1384 (3fe24e7d03d0 @ 589)
I'm not sure what the conditions are for that screen showing or failing to show (usually the latter in my experience), but your journal.txt says:
Dec 08 09:46:19 robot gnome-shell[ 1637760] : Error in freeze/thaw accounting 1637760] : GNOME Shell crashed with signal 5 1637760] : == Stack trace for context 0x55d585a44220 == 1637760] : #0 55d585f7f1d8 i resource: ///org/ gnome/shell/ ui/windowManage r.js:1384 (3fe24e7d03d0 @ 589)
Dec 08 09:46:19 robot gnome-shell[
Dec 08 09:46:19 robot gnome-shell[
Dec 08 09:46:19 robot gnome-shell[
so that's bug 1897765.