It appears that lists start with index number 0 on the Project Detail Page, but with 1 anywhere else (i.e. Preview, Live Test). This bug affects, and possibly breaks, all apps with lists on the Project Detail Page. I’ve made a couple of simple apps that showcase the bug (using S2P and DnD). Just open each app on the Project Detail Page and then remix it to see the difference:
Hey all, we saw this too and are working on a fix. It will. be updated soon.
For now, if you plan on sharing your project page as the main way of distributing the app, you probably want to use an index of (item # - 1) until the fix has been pushed out.