mkvpropedit fails to add new chapters to an "only-chapter.mkv" file

Hi Mosu

I have simple loaded a chapter.xml file (output tab) and mux it to a chaps.mkv file.

Now I want to change the chapters via mkvpropedit:

mkvpropedit.exe chaps.mkv -c new_chaps.xml

This fails and I get an error message: a level 1.Element could not be found.

chaps.7z

I have attached test files for a faster first overview.

With MkvToolNixGUI Chapter Editor is it possible to add/change the new chapters. But there is no info after clicking the menu item "Save to Matroska ...."