Atualizei meu aplicativo para oferecer suporte ao iOS 7 e enfrentei o problema de uma tela da minha[context save]; Estou tendo o erro a seguir:

NSCocoaErrorDomain Code=133020 "The operation couldn’t be completed. (Cocoa error 133020.)" UserInfo=0x1115a6d0 {conflictList=(
"NSMergeConflict (0x1115a670) for NSManagedObject (0xf25c850) with objectID '0xf25c070 <x-coredata://76AF57C8-F7FF-4880-B06B-63F8B780C96D/Screen/p7>' with oldVersion = 5 and newVersion = 6 
and old object snapshot = {\n    index = 3;\n    message = \"<null>\";\n    status = 0;\n} and new cached row = {\n    index = 3;\n    message = \"<null>\";\n    status = 0;\n}"

No iOS6 este problema não ocorre.

Atualização: código para managedObjectContext

-(NSManagedObjectContext *)managedObjectContextForCurrentThread{
if ([NSThread isMainThread])
{
    NSManagedObjectContext *parentContext = self.mainManagedObjectContext.parentContext;
    [parentContext performBlockAndWait:^{
        NSMergePolicy *mergePolicy = [[NSMergePolicy alloc] initWithMergeType:NSMergeByPropertyObjectTrumpMergePolicyType];
        [[self mainManagedObjectContext] setMergePolicy:mergePolicy];
    }];
    return self.mainManagedObjectContext;
}
else
{
    NSMutableDictionary *threadDict = [[NSThread currentThread] threadDictionary];
    NSManagedObjectContext *threadContext = [threadDict objectForKey:kCGMManagedObjectContextKey];
    if (threadContext == nil)
    {
        threadContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType];
        NSManagedObjectContext *parentContext = self.mainManagedObjectContext.parentContext;
        [parentContext performBlockAndWait:^{
            NSMergePolicy *mergePolicy = [[NSMergePolicy alloc] initWithMergeType:NSMergeByPropertyObjectTrumpMergePolicyType];
            [parentContext setMergePolicy:mergePolicy];
        }];
        [threadContext setParentContext:self.mainManagedObjectContext];
        [threadDict setObject:threadContext forKey:kCGMManagedObjectContextKey];
    }
    return threadContext;
}

}