Short Titles in book (Koma-script)

Hi I wrote my thesis in Lyx. Some of my chapter titles are quite long, so I'd like to use short titles to appear in the page headers. If I add the optional short title to a chapter and then only compile the chapter, it works fine. Also the latex code looks how it should:

Short Titles in book (Koma-script)

Hi I wrote my thesis in Lyx. Some of my chapter titles are quite long, so I'd like to use short titles to appear in the page headers. If I add the optional short title to a chapter and then only compile the chapter, it works fine. Also the latex code looks how it should:

Short Titles in book (Koma-script)

Hi I wrote my thesis in Lyx. Some of my chapter titles are quite long, so I'd like to use "short titles" to appear in the page headers. If I add the optional short title to a chapter and then only compile the chapter, it works fine. Also the latex code looks how it should: