Facet select created, but reference to it is not

1) In the CMS I wanted to change an external link to an internal link.
2) I selected the external link,
3) clicked on the internal link button
4) and choose the desired internal link.
5) Then I wanted to save a document, but I got errormessages about mandatory fields not being filled, while that was not true.
6) As a workaround I filled all empty (non-mandatory) Xinha fields with a point and tried to save again.
7) This time, this workaround failed
8) In the console I found that the draft contains the newly made facet select, but not the reference to it. The href in the Xinha field is still the external link.

I attach an export of the handle containing the live and draft variants. The facet select is called 'index' and the external link is http://www.onehippo.org/cms7/delve_into/user/information_architects/index.html. The internal document that I linked to is /content/documents/docs/cms/learn/user/information_architects/index and has uuid f6eb8141-70b8-4123-b834-b74c528ea2bd, so the docbase of the facet select is correct.

This problem about the mandatory fields has occurred before after I tried to change an external field to an internal field, but then I did not notice that that may be of importance.