Translation text before <mrk> tag in sdlxliff

We regulary experience the following problem in SDLXLIFF files: Translation text *before* the <mrk> tag (which is not even visible in the Studio Editor).
It’s always the first segment.

Example:

<trans-unit id="7ad28abe-0e8e-469e-a458-0969f9caa1a0">
<source>General Description of the Production Line</source>
<seg-source><mrk mtype="seg" mid="1">General Description of the Production Line</mrk></seg-source>
<target>Allgemei<mrk mtype="seg" mid="1">Allgemeine Beschreibung der Produktionslinie</mrk></target>
</trans-unit>

Result after export:
<title>AllgemeiAllgemeine Beschreibung der Produktionslinie</title>

What could the problem be? The translator starting to type too fast..? In the Editor, only the correct text is visible:
Allgemeine Beschreibung der Produktionslinie

Thanks in advance for any feedback...