Pinned children that aren't visible are lost on saving

Steps to reproduce:

1. Go to a space with more than 20 children, for example, enable hidden pages and go to the XWiki space.
2. Go to the children viewer and open the pinned child pages tab
3. Click on the "more" item at the bottom of the tree.
4. Pin a page in the now loaded items like "Attachments JSON Service" in my example (see attached video).
5. Click "Save".
6. Reload the page.
7. Re-order one of the visible pages (don't click on "more")
8. Click "Save"
9. Reload the page.
10. Click on the "more" item at the bottom of the page.

Expected result:

The page that has been pinned in step 4 and all pages before it are still pinned.

Actual result:

None of the pages loaded after clicking on "more" is pinned.

I've attached a video to demonstrate this.