How can I force Vaadin v8 to update the screen?

I had the same problem, see below how it could be done in version 8.0.5 (from 2017):

@Push
public class WebUi extends UI {
   public void fireComponentUpdated() {
      getUI().push();
   }
}

Is the first ComboBox in "immediate" mode?

If not, it probably should be : component.setImmediate(true).

See https://vaadin.com/book/-/page/components.selection.html

Related