Redirect not redirecting

This page: https://www.domme-chronicles.com/worksheet-femdom-series-3-how-to-make-your-first-bdsm-scene-amazing

Is set up to redirect to: https://www.domme-chronicles.com/redirects/bdsm-scene-planner.php [this php file contains a simple url address].

But it only works when I’m logged into wp-admin, not incognito and not for my testers.

I also tried redirecting to a simple url (in case redirecting to a php file was causing a problem) with the same result.

The redirect shows up in the log as if it’s working, but it doesn’t do anything.

I have other older redirects that work fine.

The only difference with this one is that the source URL is a media attachment page. I can’t see why that would cause problems but there is nothing else unique about that page.

I feel as if I must be missing something fundamental here because it’s not like it’s complicated!

Any ideas?

Thanks.

The page I need help with: [log in to see the link]