[Doitsu]

This behavior is caused by the style that you've assigned to the link targets:

 <h2 class="hide" id="sigil_toc_id_13">Absenz</h2>

.hide {display:none;}

Basically, you've created links to invisibe = non-existing targets.

You might want to change this to:

from:

  <h2 class="hide" id="sigil_toc_id_13">Absenz</h2>

  <p><strong>Absenz</strong> · Abwesenheit · Defizit · Fehlen</p>

to:

  <p id="sigil_toc_id_13"><strong>Absenz</strong> · Abwesenheit · Defizit · Fehlen</p>