IOS CoreData image issues when working with a backup

We have an application that allows users to create their own content, which includes "groups" of text and images that are then used in the game. They are written to the db, but are also "restored" back to documents when they are "synchronized" or "backed up" with an existing or "clean" device.

User can back up (.fgz) to Dropbox, making it easy to share game data across multiple devices. This works without issue. Game content (db driven) and images can be shared across any number of devices without problem.

Every time we update the app, we have a problem where the text entries are being fetched and fully viewable (both from the local file system / sqlite) and for some reason the images in the same location are not showing as they were previously (image path seems out of date during update). This includes doing a "backup" to a newer version of the application on a device that has not previously installed the application, which is also very strange.

During testing, using Xcode and local copies (by replicating "install in place" we cannot replicate this issue using the same code and databases. There are no errors or warnings. Is this a major data problem? Suggestions that we can we do wrong?

What's going on here? We are trying to find a solution for our purposes. Is there a better way to do this? We thought about keeping our files only on the local filesystem, but if we do, they won't be "shared" via the dropbox.

Any thoughts on managing image data in iOS would be much appreciated.