We found that drag and drop is buggy in both 1.9 and 2.0 versions. The topic body moves independently without the heading. So until you refresh the page, the topic headings are all wrong.
I have fixed the 1.9 version and am working on 2.0. I'm sure there is a better way of doing this, but I am attaching my patch files for info.
The problem lies in the fact that drag and drop looks for ids matching 'section-<n>'. In most formats the element with this id wraps the entire week/topic. However in this format it only wraps the content.