I have an entity like this:

public class Survey : EntityBase 
{
    protected Survey() 
    {
    }

    public Survey(long id, int version, string title, long userId, string phone)  
    {
        Id = id;
        CreationTimeUtc = DateTimeOffset.UtcNow;
        Version = version;
        Title = title;
        UserId = userId;
        Phone = phone;
        Status = SurveyStatus.Initial;
        IsDeleted = false;
        Questions = new List<SurveyQuestion>();
        Feedbacks = new List<SurveyFeedback>();
    }

    public int Version { get; protected set; }
    public long UserId { get; protected set; }
    public string Phone { get; protected set; }
    public string Title { get; protected set; }
    public SurveyStatus Status { get; protected set; }
    public bool IsDeleted { get; protected set; }

    public ICollection<SurveyQuestion> Questions { get; protected set; }
    public ICollection<SurveyFeedback> Feedbacks { get;  protected set; }

    public void AddQuestion(SurveyQuestionAddedEvent @event) 
    {
        var question = new SurveyQuestion(@event.QuestionId, @event.CreationDateTimeUtc, @event.AggregateId, null, @event.Order, @event.Description, @event.MultiSelectOption,
        @event.Options.Select((t, i) => new SurveyOption(@event.QuestionId, t.Key, i + 1, t.Value)).ToList()
                            );
        Questions.Add(question);
        Version = @event.Version;
        ModificationTimeUtc = @event.CreationDateTimeUtc;
    }
}

And SurveyQuestion is this:

public class SurveyQuestion : EntityBase 
{
    private SurveyQuestion() 
    {
    }

    public SurveyQuestion(long questionId, DateTimeOffset creationTimeUtc, long surveyId, long? parentId, byte order, string question, bool multiSelectOption, ICollection<SurveyOption> options) 
    {
        Id = questionId;
        CreationTimeUtc = creationTimeUtc;
        SurveyId = surveyId;
        ParentId = parentId;
        Order = order;
        Question = question;
        MultiSelectOption = multiSelectOption;
        Options = options;
    }

    public long SurveyId { get; protected set; }
    public long? ParentId { get; protected set; }
    public byte Order { get; protected set; }
    public string Question { get; protected set; }
    public bool MultiSelectOption { get; protected set; }
    public ICollection<SurveyOption> Options { get; protected set; }
}

And I have a repository:

public class SurveyRepository : RepositoryBase<Survey>, ISurveyRepository 
{
    public SurveyRepository(EntityContext context) : base(context) 
    {
    }

    public async Task AddAsync(Survey survey) => await Set.AddAsync(survey);

    public async Task<Survey?> FindByIdAsync(long id)
        => await Set.AsNoTracking()
                    .Include(t => t.Questions)
                    .ThenInclude(t => t.Options)
                    .FirstOrDefaultAsync(t => t.Id == id);

    public async Task AddQuestionAsync(Survey survey, SurveyQuestionAddedEvent @event) 
        => await Task.Factory.StartNew(() => {
               survey.AddQuestion(@event);
               Set.Update(survey);
           });
}

And the RepositoryBase class is:

public abstract class RepositoryBase<T> : IRepositoryBase<T> where T : EntityBase
{
    protected RepositoryBase(DbContext context) 
    {
        Set = context.Set<T>();
    }

    public DbSet<T> Set { get; private set; }
}

In Service class I find a Survey by id that Question property is empty (count = 0).

When I add a question in collection of questions in survey questions, tracker set question to modify instead of Add.

Why is this happening?

I can change EntityState manually but I imaging EF Core should solve this problem.