Subheader Title is empty

For some reason the pagetitle is not showing in the subheader. The only exception is the blog start page.

The DOM looks like this:

<div id="Subheader"><div class="container"><div class="column one"><h1 class="title"></h1></div></div></div>

But the title itself appears in the title of the browser tab:

<title itemprop="name">Unterricht | Schola Bohemica</title>

link to site with missing title:

http://develop.schola-bohemica.de/de/unterricht/ 

link to site with showing title (blog page)

http://develop.schola-bohemica.de/de/aktuelles/

"Subheader | Hide" in Themeoptions > Header & Subheader > Subheader is unchecked.

Thanks in advance for your help!