Steps to reproduce

(Steps 1-6 are used to reproduce an instance the page content has been messed up by past edits)

1. create a page and insert page layouts on them
2. save the page
3. edit the page
4. Right click on the editor pane and click inspect element
5. Transverse the DOM until you can find <div class="contentLayout2">
6. Replace this div and its contents with the contents of the attached "twoLayouts.html" - this contains html that replicates page content that has two contentLayouts
7. save the page

The page will look fine. All the content will render okay. However, if the user attempts to remove one of the sections, both the sections will be removed.
If the user attempts to move one section up or the other section down, the editor will not respond.