I think that reason is in managedObjectContext. You make changes in background, and NSFetchedResultsController fetches from the main one. So you need to merge changes to that one context by adding an observer of changes in context.
I would suggest, when using UIManagedDocument, that you make your background context a child of the main context.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.