When clicking on subpages directly, say Page 2, it looks “clean” and pagination is set correctly. However, trying to press “next” or choose say Page 3, the problem persists - the next button doesn’t work and choosing page 3 for example, adds a paged URL to that page example /page/2/?_paged=3
I modified the code a bit for my own setup and added a check to see if post type is set because it caused some errors on other pages/queries but now the pagination works and the new pages load as expected.
For SEO, this is not necessarily problematic, as long as all individual posts are reachable for the search engine spider through other archive pages on the site, like post-type archives and term archives. Another way to make sure all pages are found is by implementing a sitemap and pointing to it in your robots.txt file.