Right now the H1 on the 404 error page is tagged as text, not a heading. This is causing it fail to accessibility checkers and is prompting SEO issue reports in Bing Webmaster and Google Search Console, since any failed redirect link points to the 404 page.
Maroyafaied
commented
1 year ago 
Might relate to issue#2493
Right now the H1 on the 404 error page is tagged as text, not a heading. This is causing it fail to accessibility checkers and is prompting SEO issue reports in Bing Webmaster and Google Search Console, since any failed redirect link points to the 404 page.
https://www.onrr.gov/404