Blog page renamed "Blog Full Width"

Hi gang!

In Settings -> Reading I set my “Posts” page to “Blog” and it now says “Blog Full Width” as the page title (the element is <h1 id="page-title">). The page title in the top of my browser window is still correct as simply “Blog”

This is a client’s site that was previously built and edited. Any ideas where I might find the bit of code to fix this? I checked the “page.php” and “header.php” files and “style.css”. I’m using a child theme and if I remove the “Blog” page as the “Posts” page it goes back to just saying “Blog”, but then it shows the same 5 posts every page.

Thanks in advance!