Do you have the page on which I can see the issue online?

I meant:
Please give me the url of the page you are using Articles Field on so I can see the issue.

The urls are generated through the Joomla router. So not sure why they would not be ok.

Can you give me (super) admin and (s)ftp access so I can take a look?
And tell me on what url I can see/reproduce the issue.

7 months later... 🙂

Also, which Field does this concern?

Looks like there is something wrong with the routing of articles on your setup.

Articles Field asks Joomla for the content URL, which results in:That's all good.
Then it asks Joomla to route that URL to a link URL (SEF), which results in:Which is not good.

This is outside the control and responsibility.

You can see the issue too now on that URL outside of Articles Field.

I simply created a link to that book directly inside the article contents, using the core 'Article' editor button.
It too uses that same incorrect SEF url.

I don't know. Like I said, it as not an issue of Articles Field. But something weird in your set-up. Or in Joomla itself.

I recommend you ask around on the Joomla forum:
forum.joomla.org