Vaadin 14 - iFrame reloads endlessly

I’m trying to display a second Vaadin 14 application in my Vaadin 14 application via Iframe.

This is where I get problems. The application reloads endlessly!

The PushHandler is called in the backend … Apparently the session does not match the requestToken …
Is it possible to use Vaadin to display a Vaadin application in the iframe?

Many thanks