By "brought down" do you mean crash or (the usual) repainting stopped?

If the second one, it starts to look like yet another xwayland bug (assuming you run wayland - I think you do). Log clearly shows that I call gdk_window_invalidate_rect with proper parameters (it is the INVALIDATE word in the log), after which gtk is supposed to call me back and do the repaint (GtkDraw in the log). Log shows the repaint properly happens at the beginning, but then stops doing so near the end of log....

Anyway, I have added even more logging, so please one last time pull logs branch and keep testing...