(In reply to Marek Olšák from comment #22)
> How do I reproduce the Xfce hang and corruption? It's not reproducible with
> Ubuntu 16.04.

How old is XFCE in 16.04? I'm using 4.14, which was released this month. 

Here's a quote from the release notes: "The window manager received a slew of
updates and features, including support for VSync (using either Present or
OpenGL as backend) to reduce or remove display flickering, HiDPI support,
improved GLX support with NVIDIA proprietary/closed source drivers, support for
XInput2, various compositor improvements and a new default theme." Maybe older
versions of the window manager don't trigger the issue.

Either way, I have an extra SSD on the way. I should be able to swap that in to
the machine and figure out some directions for reproducing the bug from a clean
install.