When trying to delete a patron group that is "in use", we get the usual modal alert with a message like "Can not delete group, 52 users associated with it." It also removes the patron group entry from the screen (it looks like it got deleted anyway.)
Upon navigating away from the screen, we get a "There are unsaved changes" dialog. If you click "Cancel", the box disappears but you need to go out of the current screen to display the deleted entry again. This doesn't seem right to me.
I think it would be a desirable user experience to not have to be presented with two kinds of dialogs.