I am in version 7.12, and I have been trying to use the replace data source from the data panel functionality. For various reasons, replacing the data source and/or deleting a join operation may break a join, but that isn't apparently from the data panel. You can only tell there is a problem by going to the data tab and seeing that there is just no data. Given that the data panel red flags so many other problems, it doesn't make sense that this isn't flagged.