Github Pages claiming my DNS is improperly configured

This past weekend I moved to a new static site generator, and to keep things simple I renamed my old repository and created a new one. I set up a CNAME record to point to the new one:

www.grahamwheeler.com CNAME gramster.github.io

and a CNAME file in the new repository to point to my custom domain:

www.grahamwheeler.com

But in the settings I keep seeing:

grahamwheeler.com is improperly configured
Domain does not resolve to the GitHub Pages server. For more information, see Learn more (NotServedByPagesError). We recommend you add an A record pointed to our IP addresses, or an ALIAS record pointing to gramster.github.io.

The remediation suggested above is different to what I have been doing and thought I should still be doing, namely using a CNAME. Is the process different now? If not, what is wrong with my setup?

I forgot to mention too: despite the error, my sire becomes accessible at the custom domain. However, if I push any changes then it disappears and I get a 404. Then I have to once again go to the settings for Pages, reconfigure the CNAME, ignore the error, and the site is back. This is pretty crazy.

seems the page is fine now

also, I cannot see those error logs you are mentioning at the History

https://github.com/gramster/gramster.github.io/deployments/activity_log?environment=github-pages