Multiple H1s
What it means
These pages have more than one <h1>. HTML5 permits it, but in practice several top level headings usually mean the heading hierarchy is being used for styling rather than structure.
How to fix it
Keep one <h1> for the page's subject and demote the others to <h2> or <h3> according to how they nest. Check templates first: a header logo wrapped in an <h1> plus a page title in another is the most common cause.
Finding it in CrawlStat
After a crawl, open Issues and pick Multiple H1s. Click Show all in Pages to filter the Pages table to the affected pages, or Export affected to hand the list to whoever owns the fix. Audit ID: h1_multiple.