This is performing as designed. To move items within a category, click the category name, then scroll to the bottom of the page to find the list of items. The items can be rearranged on this page.
Steps to Duplicate1. Click Management
2. Click eStore (Cart)
3. Click the plus sign next to the number of items
4. Hover over one of the items
5. Drag and drop the item to a new location; this is when the entire category moves instead of just the one item