GSC Reporting 404s on pages not on site anymore (with redirects)

Our Google Search Console is reporting 404s on a number of pages. They don't show up in Screaming Frog, aren't on the site, and aren't linked anywhere on the site!

Even some pdfs linked on the site that were switched out for other ones are now being marked as 404s. Is there any reason for this?

I'm going to double check redirects for these, but how do we stop GSC from these older, previously indexed pages.