This is a Lemmy-ui bug, not related to CDN/cache.

I had submitted a bug report for it some time ago but it’s not that urgent in the great scheme of things so they didn’t get around to it yet: https://github.com/LemmyNet/lemmy-ui/issues/1865

(the report speaks about this happening after you log in, but it’s the same thing).

Awesome project and the tool looks great - nice work!

There was an existing tool which was similar: https://federation-checker.vercel.app/

Yours is definitely nicer.