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I get a 404 page-not-found error while trying to open a child doc.

In a buddypress group i’ve created thee docs. 1 sould be the parent of the other 2. Then i’ve edited the two docs and set the partent for both. While viewing the parent doc, it displays the 2 child docs only when clicking on the link it gives me the 404. I’ve found the problem, only don’t no how to fix it… 🙁 The permalink is not prefixin the parent(slug).

Here are the given urls/permalinks of the docs;
/docs/xxx (parent)
/docs/yyy (first child)
/docs/zzz (second child)

Both childs can’t be reached/viewed, but if i prefix the url they can.

/docs/xxx
/docs/xxx/yyy
/docs/xxx/zzz

Can someone please help me out?

https://ww.wp.xz.cn/plugins/buddypress-docs/