I'm not sure which version this started in - I think it was after I updated to iOS 8, but I'm not sure. I used to be able to select photos that were in a shared Photo Stream and add them to a sync folder. Now I can select them, but as soon as I hit the check button to start syncing, the app crashes. I can still upload photos from my Camera Roll without a problem. I'm updated to 1.4.97 on 8.1 on a 5S. The crash log mentions "bug_type":"109", if that's informative.