efcore: Adding an Entity Graph with sub-n-level entities with the same Id results in error - Breaking Change

EFCore 3.1.1 - breaking change Adding a disconnected entity graph to EF Context, if there is an entity of the same type with the same Id this results in an error.

In the previous version 2.2 and in the EF6 this was working fine.

Steps to reproduce

    public class SampleContext : DbContext
    {
        public DbSet<Book> Books { get; set; }
        public DbSet<Author> Authors { get; set; }
        public DbSet<Shelf> Shelfs { get; set; }
        public DbSet<ShelfBooks> ShelfBooks { get; set; }

        public SampleContext()
            :base()
        {
            //  Detaching an entity results in related entities being deleted
            //  https://github.com/dotnet/efcore/issues/18982
            base.ChangeTracker.CascadeDeleteTiming = CascadeTiming.OnSaveChanges;
            base.ChangeTracker.DeleteOrphansTiming = CascadeTiming.OnSaveChanges;
        }
    }
    public class Author
    {
        public int AuthorId { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public ICollection<Book> Books { get; set; }
    }
    public class Book
    {
        public int BookId { get; set; }
        public string Title { get; set; }
        public Author Author { get; set; }
        public int AuthorId { get; set; }
    }
    public class Shelf
    {
        public int ShelfId { get; set; }
        public string Description { get; set; }
        public ICollection<ShelfBooks> ShelfBooks { get; set; }

    }
    public class ShelfBooks
    {
        public int ShelfBookId { get; set; }
        public int ShelfId { get; set; }
        public Book Shelf { get; set; }
        public int BookId { get; set; }
        public Book Book { get; set; }
    }
    
    public class Test
    {
        public void AddToEFC()
        {
            var shelf = new Shelf();
            shelf.ShelfId = 0;
            shelf.Description = "New Shelf";

            shelf.ShelfBooks = new List<ShelfBooks>();
            var sb1 = new ShelfBooks
            {
                ShelfId = 0,
                Book = new Book
                {
                    BookId = 100,
                    Author = new Author
                    {
                        AuthorId = 2,
                        FirstName = "Existing Author",
                        LastName = "2"
                    },
                    Title = "Existing Book1"
                }
            };

            shelf.ShelfBooks.Add(sb1);

            var sb2 = new ShelfBooks
            {
                ShelfId = 0,
                Book = new Book
                {
                    BookId = 200,
                    Author = new Author
                    {
                        AuthorId = 2,
                        FirstName = "Existing Author",
                        LastName = "2"
                    },
                    Title = "Existing Book2"
                }
            };

            shelf.ShelfBooks.Add(sb2);

            var ctx = new SampleContext();
            ctx.Shelfs.Add(shelf);      // throws error
        }
    }

Adding the shelf entity to the EFCore context results in the error: Message: The instance of entity type ‘Author’ cannot be tracked because another instance with the key value ‘{AuthorId: 2}’ is already being tracked. When attaching existing entities, ensure that only one entity instance with a given key value is attached.

StackTrace:

at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.IdentityMap`1.ThrowIdentityConflict(InternalEntityEntry entry)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.IdentityMap`1.Add(TKey key, InternalEntityEntry entry, Boolean updateDuplicate)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.StartTracking(InternalEntityEntry entry)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.InternalEntityEntry.SetEntityState(EntityState oldState, EntityState newState, Boolean acceptChanges, Boolean modifyProperties)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.EntityGraphAttacher.PaintAction(EntityEntryGraphNode`1 node)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.EntityEntryGraphIterator.TraverseGraph[TState](EntityEntryGraphNode`1 node, Func`2 handleNode)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.EntityEntryGraphIterator.TraverseGraph[TState](EntityEntryGraphNode`1 node, Func`2 handleNode)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.EntityEntryGraphIterator.TraverseGraph[TState](EntityEntryGraphNode`1 node, Func`2 handleNode)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.EntityEntryGraphIterator.TraverseGraph[TState](EntityEntryGraphNode`1 node, Func`2 handleNode)
   at Microsoft.EntityFrameworkCore.DbContext.SetEntityState(InternalEntityEntry entry, EntityState entityState)
   at Microsoft.EntityFrameworkCore.DbContext.SetEntityState[TEntity](TEntity entity, EntityState entityState)

Further technical details

EF Core version: 3.1.1 Database provider: Microsoft.EntityFrameworkCore.SqlServer Target framework: .NET 4.6.1 Operating system: Win 10 Pro 1909 IDE: Visual Studio 2019 16.4.5