The most reliable way to reproduce the freeze seems to be to activate the desktop-grid effect while a tool-tip window is fading in.
Ensure desktop-grid is configured to use present windows, and that present windows is configured to use the natural layout algorithm with the fill gaps option selected.
The freeze is still intermittent, but using this method should be able to be triggered within about 10 tries without this fix.
After applying the fix, the freeze has never been observed.