Missing chapter markers in export to iDVD

I have a project which is approx 20 minutes long and contains only jpg image files and audio from iTunes. It has 7 chapter markers with the first chapter positioned after the intro frame. The audio files run through i.e. across these video chapter markers. The project when burnt using iDVD has 'lost" these markers. How can they be reinstated?

As a later (same day) addition to this post I duplicated the project, renamed it, deleted all the audio and sent it to iDVD again. The same problem is evident i.e. that the chapter markers are not being recognised, there is no sub menu created to accommodate them and so they are a missing feature of the final DVD.

Does anyway know how to overcome this issue?