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As I understand it, the way Moz crawls means it won't pick up HTML that is added dynamically. Without knowing which site you are talking about, I can't check, but I worked with a client who had a site that dynamically generated areas of the page after the first draw and that caused some issues with the Moz crawler correctly identifying issues on the site. I would suggest checking with Search Console "Fetch as Google" tool just to make sure Google is "seeing" the page correctly, and, if so, ignore the alerts in Moz.