I have just extracted the latest Joomla 4 Stark quickstart bundle on my localhost. When I display a T4 Page Builder page in the component, the top menu in blue suddenly appear. This blue top menu does not appear in the other pages in the Stark quickstart website. So, there must be some clash between the Stark website and the T4 Page Builder.
I am running the Joomla 4 Stark quickstart site on PHP 7.4.24 MAMP packaged by Bitnami. See attached screenshot for reference.
Please do not ask for live website as there is none. I'm running this on localhost.