Bug#854373: kwin-x11: kwin sometimes hangs with 100% cpu for kwin_x11

[Karl Heisenberg]

   I experience the same bug with the latest debian-sid:
kwin_x11 5.13.1-1+b1nvidia 390.77-1
the freeze is about every 1-2 hours, and it takes 1-2 minutes to restart kwin 
since also switching to terminal by ctrl-alt+f1 is delayed.
Very annoying bug...