Web page does not render if load() is called early

Using the Qt WebEngine Widget simple browser example.

Running the simplebrowser works fine and displays qt.io page.

Adding load({"http://www.google.com"}) in the WebPage class constructor changes the behavior:

• simplebrowser loads qt.io in the first tab, but the page is not rendered => nothing is displayed on screen
• Opening a new tab loads google.com, but the page is not rendered.
• Switching tab does not change anything
• Typing a new URL in any of the 2 tab loads the new URL and render the page
• Going back to the other tab still shows an empty grey area where nothing was rendered

I was able to reproduce the behavior on a personal project that has a single QWebEngineView and changes its page when changing tab.

If I add a child widget to QWebEngineView it is usually not visible, hidden by the web page.
When I reproduce this bug, I can see the child widget.