para-section-para

While preparing an article in the following format I receive a not allowed instruction.
Editor: Oxygen 10.3

<article xmlns="http://docbook.org/ns/docbook"

    xmlns:xlink="http://www.w3.org/1999/xlink" version="5.0">

  <section>

    <para>text</para>

    <section>

      <para>text</para>

    </section>

  <para>text</para> (This paragraph shows as not allowed. Why?)

  </section>

</article>

Exports to the browser fine.

Must I follow a <section> with a <section>, that works, but this would break up the flow of the document, which is an old report.

Or is this a bug?