On my W520 ThinkPad I've disabled my touchpad using Gnome Settings, and so far this bug hasn't occured. Although this doesn't resolve this underlying issue, it makes the desktop usable again.
Considering that this bug is touchpad related, using an external mouse and disabling the touchpad could work for anyone. In 2 days time the new version of libinput should land in Buster, so then I can verify this issue is resolved.
