Spoke to wpbakery and they said…
“The https://www.domainhidden.com/wp-sitemap.xml is a page generated by sitemap plugin and WPBakery Page Builder does not have any control over it. The WPBakery Page Builder can only work on static pages while the generated pages are controlled by the respective plugins and the theme.
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I did mention before that if I disable AIO SEO, the issue goes away, i.e. wp-sitemap.xml doesnt throw out a load of gibberish.
I love AIO SEO. I love WPBakery. But when both say ‘its not us, its them’ its very frustrating as I then have zero idea how to resolve.