Umlaute are not represented correctly (not always)

• Testcase included:

  yes

The german umlauts (äöüß) are not represented correctly. Instead of it appears # symbol. But not always.
The items from Document Descriptor are represented correctly. For instance: in document descriptor we have

<toc name="Table of Contents">
<item name="Übersicht" ref="/30-documentation/0-uebersicht.apt"/>
</toc>

In 0-uebersicht.apt we have a line: Übersicht test äöüß ÄÖÜ
The output looks: #bersicht test #### ###. See also attachment.