"Cannot run layout while processing state change from the server" Warning in MPR

[TobseF]

In our Vaadin 8 - Vaadin 14 Multiplatform Runtime (MPR) project we get a JS warning on every page:

Cannot run layout while processing state change from the server

This warning is defined in:
https://github.com/vaadin/framework/blob/ba02350206ef25f6c29618f3cf7458f43543f3e8/client/src/main/java/com/vaadin/client/LayoutManager.java#L42

Problem

• What are the implications when we use our application with this warning?
• How can we get rid of it?

Set-Up

To reproduce simply set up a MPR application and add Vaadin-8 component by wrapping it with the LegacyWrapper.

@Route(value = "sample")
@MprTheme("frontend")
@LegacyUI(SampleUI.class)
@MprWidgetset("com.vaadin.addons.widgetsets.AddonWidgetset")
@Push
public class SampleApplication extends Div {

	public SampleApplication() {
		add(new H1("Sample Application"));
		com.vaadin.ui.Button oldButton = new com.vaadin.ui.Button("Old V8 Button");
		add(new LegacyWrapper(oldButton));
	}
}

Versions

Vaadin 14 version: 14.6.0
Vaadin 8 version: 8.12.4
Vaadin Flow Plugin version: 2.4.6
Browser version: Chrome 90.0.4430.212
Java version: 14.0.2
Push: enabled by @Push-annotation
Server running with: vaadin.productionMode = false