EF Core Tracking Error while adding a record into database

Question

I have the following classes and methods to add an appointment:

public async Task<bool> UpdatePatientAppointmentAsync(AppointmentData appointment)
{
    int res = 0;

    using (var scope = _scopeFactory.CreateScope())
    {
        var context = scope.ServiceProvider.GetRequiredService<ApplicationDbContext>();

        // appointment.AppointmentId = 0;
        try
        {
            context.Appointments.Add(appointment);

            res = await context.SaveChangesAsync();

            if (res > 0)
                return true;
            else
                return false;
        }
        catch (Exception ex)
        {
            return false;
        }
    }
}

public async Task<List<AppointmentData>> GetPatientAppointmentsAsync(Patient patient)
{
    using (var scope = _scopeFactory.CreateScope())
    {
        var context = scope.ServiceProvider.GetRequiredService<ApplicationDbContext>();
        var appts = await context.Appointments
                                 .Include(d => d.Doctor)
                                 .Include(d => d.Patient)
                                 .AsNoTracking()
                                 .Where(p => p.PatientId == patient.PatientId)
                                 .ToListAsync();

        DisplayStates(context.ChangeTracker.Entries());

        return appts;
    }
}

public class Doctor
{
    [Key]
    public int DoctorId { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string Specialization { get; set; }
    public string Phone { get; set; }
    public string Email { get; set; }
    public string Designation { get; set; }
    public bool IsDeleted { get; set; }
}

public class AppointmentData
{
    [Key]
    public int AppointmentId { get; set; }
    public string Subject { get; set; }
    public string Location { get; set; }
    public DateTime StartTime { get; set; }
    public DateTime EndTime { get; set; }
    public string Description { get; set; }
    public string EventType { get; set; }
    public bool IsAllDay { get; set; }
    public string RecurrenceRule { get; set; }
    public string RecurrenceException { get; set; }
    public Nullable<int> RecurrenceID { get; set; }
    public int PatientId { get; set; }
    public Patient Patient { get; set; }
    public int DoctorId { get; set; }
    public Doctor Doctor { get; set; }  
}

I load appointments and doctors as follows:

protected override async Task OnInitializedAsync()
{
    appointments = await DataService.GetPatientAppointmentsAsync(AppState.SelectedPatient);
    doctors = await DataService.GetAllDoctorsAsync();
}

and then save an appointment like this:

appt.Patient = AppState.SelectedPatient;
appt.PatientId = AppState.SelectedPatient.PatientId;
appt.Doctor = doctors.First(d => d.DoctorId == Int32.Parse(fn));
appt.DoctorId = Int32.Parse(fn);

var res1 = await DataService.UpdatePatientAppointmentAsync(appt);

DataService is registered as follows:

builder.Services.AddScoped<DataService>();

When UpdatePatientAppointmentAsync is called, I get the following EF Core error:

The instance of entity type 'Doctor' cannot be tracked because another instance with the same key value for {'DoctorId'} is already being tracked. When attaching existing entities, ensure that only one entity instance with a given key value is attached.
Consider using 'DbContextOptionsBuilder.EnableSensitiveDataLogging' to see the conflicting key values.

I don't want to update or track the Doctor entity and I don't understand why it's being tracked. When loading all data, I am using .AsNoTracking(). Is it possible to turn off tracking for Doctor entity? Or any other pointers as how to resolve this error?