It sounds like you might have two full-page images with the same title in your front matter. This creates confusion within the ePub since they will both have the same reference title. If you rename one or both of these pages, that should solve this issue.
To rename a Full-page Image, you'll want to click on that page in the Navigation Pane. With it open in the Content Editor, you can add a new title to your image by replacing the text Full-page Image.