Sorry I'm late to the game but here's how to actually fix this issue. The Apple Engineer was correct, you'll need to add this flag to your scheme. -com.apple.CoreData.ConcurrencyDebug 1 Xcode->Scheme->Edit Scheme->Arguments Tab With the flag enabled, your code will break every place there is a concurrency issue with Core Data. The likely fix for this is to, (As the engineer pointed out) use perform or performAndWait where your NSManagedObjectContext is called. func save() { context.performAndWait { do { try context.save() } catch let error{ // Handle Error } } }