The example code for additional elements here https://doc.smpte-doc.org/html-pub/main/#sec-annex-section
<section id="sec-elements">
<ol>
<li>
<a id="element-sample-text" title="Description of the element" href="./elements/form.docx"></a>
</li>
</ol>
</section>

gives error when rendering:
'Relative links listed in the Elements Annex must start with 'elements/'
changing the example
href="./elements/form.docx">
to
href="elements/form.docx">
seems to fix the problem
The example code for additional elements here https://doc.smpte-doc.org/html-pub/main/#sec-annex-section
gives error when rendering:
'Relative links listed in the Elements Annex must start with 'elements/'
changing the example
href="./elements/form.docx">
to
href="elements/form.docx">
seems to fix the problem