iOS 13.4 CoreData SwiftUI app crashes with "EXC_BREAKPOINT (code=1, subcode=0x1f3751f08)" on device

A very simple CoreData app: All code provided below.

• Start up with CoreData template single view app.
• 2 entities with a string attribute each: Message(title) and Post(name)

A NavigationView containing

• NavigationLink to a list of messages
• NavigationLink to a list of posts

Each linked ListView (Message/Post) has

• a button to add an item to the list
• a button to remove all items from the list

Now, when you run this app on a simulator (any iOS 13.x version) all runs as expected from the description above.

But on a DEVICE running iOS 13.4

• Tap "Messages"
• Creating/deleting messages works fine, SwiftUi view updates immediately.
• Tap "back"
• Tap "Messages" again. While still creating/deleting messages works fine: The debugger now shows a warning: "Context in environment is not connected to a persistent store coordinator: NSManagedObjectContext: 0x280ed72c0
• Tap "Posts" ==> App crashes with EXC_BREAKPOINT (code=1, subcode=0x1f3751f08)

You can start the process with Posts first, too. Then the same crash occurs on the messages list view.

I strongly believe this is an iOS 13.4 bug because similar code ran fine on Xcode 11.3 / iOS 13.3.

Does anyone know a fix or workaround for this?

Here is a link to the full project: Full Xcode Project

The ContentView:

import SwiftUI
import CoreData


struct MessageList: View {
  @Environment(\.managedObjectContext) var moc
  @FetchRequest(entity: Message.entity(), sortDescriptors: [])
  var messages: FetchedResults<Message>

  var body: some View {
    List() {
      ForEach(messages, id: \.self) { message in
        Text(message.title ?? "?")
      }
    }
    .navigationBarItems(trailing:
      HStack(spacing: 16) {
        Button(action: deleteMessages) {
          Image(systemName: "text.badge.minus")
        }
        Button(action: addMessage) {
          Image(systemName: "plus.app")
        }
      }
    )
  }
  func addMessage() {
    let m = Message(context: moc)
    m.title = "Message: \(Date())"
    try! moc.save()
  }
  func deleteMessages() {
    messages.forEach {
      moc.delete($0)
    }
  }
}

struct PostList: View {
  @Environment(\.managedObjectContext) var moc
  @FetchRequest(entity: Post.entity(), sortDescriptors: [])
  var posts: FetchedResults<Post>

  var body: some View {
    List {
      ForEach(0..<posts.count, id: \.self) { post in
        Text(self.posts[post].name ?? "?")
      }
    }
    .navigationBarItems(trailing:
      HStack(spacing: 16) {
        Button(action: deletePosts) {
          Image(systemName: "text.badge.minus")
        }
        Button(action: addPost) {
          Image(systemName: "plus.app")
        }
      }
    )
  }
  func addPost() {
    let p = Post(context: moc)
    p.name = "Post \(UUID().uuidString)"
    try! moc.save()
  }
  func deletePosts() {
    posts.forEach {
      moc.delete($0)
    }
    try! moc.save()
  }
}


struct ContentView: View {
  @Environment(\.managedObjectContext) var moc

  var body: some View {
    NavigationView {
      VStack(alignment: .leading){
        NavigationLink(destination: MessageList()) {
          Text("Messages")
        }.padding()
        NavigationLink(destination: PostList()) {
          Text("Posts")
        }.padding()
        Spacer()
      }
    }.navigationViewStyle(StackNavigationViewStyle())
  }
}

struct ContentView_Previews: PreviewProvider {
  static let moc = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
  static var previews: some View {
    ContentView()
      .environment(\.managedObjectContext, moc)
  }
}

Screenshot of the Model:

The SceneDelegate (unaltered from template, provided for completeness):

class SceneDelegate: UIResponder, UIWindowSceneDelegate {

  var window: UIWindow?

  func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {

    let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
    let contentView = ContentView().environment(\.managedObjectContext, context)

    if let windowScene = scene as? UIWindowScene {
        let window = UIWindow(windowScene: windowScene)
        window.rootViewController = UIHostingController(rootView: contentView)
        self.window = window
        window.makeKeyAndVisible()
    }
  }

  func sceneDidDisconnect(_ scene: UIScene) {}
  func sceneDidBecomeActive(_ scene: UIScene) {}
  func sceneWillResignActive(_ scene: UIScene) {}
  func sceneWillEnterForeground(_ scene: UIScene) {}
  func sceneDidEnterBackground(_ scene: UIScene) {
    (UIApplication.shared.delegate as? AppDelegate)?.saveContext()
  }
}

The AppDelegate (unaltered from template, provided for completeness):

import UIKit
import CoreData

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

  func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
    return true
  }

  func application(_ application: UIApplication, configurationForConnecting connectingSceneSession: UISceneSession, options: UIScene.ConnectionOptions) -> UISceneConfiguration {
    return UISceneConfiguration(name: "Default Configuration", sessionRole: connectingSceneSession.role)
  }

  func application(_ application: UIApplication, didDiscardSceneSessions sceneSessions: Set<UISceneSession>) {}

  // MARK: - Core Data stack

  lazy var persistentContainer: NSPersistentCloudKitContainer = {
    let container = NSPersistentCloudKitContainer(name: "Coredata134")
    container.loadPersistentStores(completionHandler: { (storeDescription, error) in
      if let error = error as NSError? {
        fatalError("Unresolved error \(error), \(error.userInfo)")
      }
    })
    return container
  }()

  func saveContext () {
    let context = persistentContainer.viewContext
    if context.hasChanges {
      do {
        try context.save()
      } catch {
        let nserror = error as NSError
        fatalError("Unresolved error \(nserror), \(nserror.userInfo)")
      }
    }
  }
}