I have an app that uses the entity framework. I have 2 DB contexts, one for the live sql database and another using InMemory for users to demo the site without changing the live db. The problem is when I add new entries to a table, the 2nd time I try I get this error.

InvalidOperationException: The instance of entity type 'ApplicationUser' cannot be tracked because another instance with the same key value for {'Id'} 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’m configuring the DB contexts like this

        services.AddDbContextPool<AppDbContext>(options =>    
        options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));

        var databaseName = new Guid().ToString();
        services.AddDbContext<DemoDbContext>(options =>
        options.UseInMemoryDatabase(databaseName), ServiceLifetime.Scoped);

        services.AddIdentity<ApplicationUser, IdentityRole>(config =>
        {
            config.Password.RequiredLength = 6;
            config.Password.RequireDigit = false;
            config.Password.RequireUppercase = false;
            config.Password.RequireNonAlphanumeric = false;
            config.User.RequireUniqueEmail = true;
        })
            .AddDefaultTokenProviders()
            .AddEntityFrameworkStores<AppDbContext>();

I’m also using AsNoTracking when getting data for the demo user

public IEnumerable<Ticket> GetTicketsForUserRole(ApplicationUser user)
    {
        return _demoDbContext.Ticket.AsNoTracking()
            .Include(ticket => ticket.Author)
            .Include(ticket => ticket.Priority)
            .Include(ticket => ticket.State)
            .Include(ticket => ticket.Project)
            .Include(ticket => ticket.Type)
            .Include(ticket => ticket.AssignedUser)
            .Include(ticket => ticket.Comments)
                .ThenInclude(c => c.User)
            .Include(ticket => ticket.Attachments)
                .ThenInclude(a => a.User);
    }

I don’t get the error when using the normal login and appDbContext.
This is where the issue occurs

 [HttpPost]
    public async Task<IActionResult> AddComment(TicketsViewModel viewModel)
    {
        if(viewModel.TicketId != null)
        {
            var applicationUser = await _userManager.GetUserAsync(User);
            var roleObject = _roleFactory.GetRole(applicationUser);

            var ticket = roleObject.GetTicketsForUserRole(applicationUser)
                .First(t => t.Id == viewModel.TicketId);

            viewModel.Ticket = ticket;

            var comment = new Comment
            {
                Date = DateAndTime.Now,
                TextComment = viewModel.TextComment,
                User = applicationUser
            };

            ticket.Comments.Add(comment);
            roleObject.UpdateTicket(ticket);

            return RedirectToAction("Details", new { id = viewModel.Ticket.Id });
        }

        return NoContent();
    }

When I add the first comment it’s ok, then I get the error when adding a second.
I am updating the ticket correctly?

public void UpdateTicket(Ticket ticket)
{
    _demoDbContext.Ticket.Update(ticket);
    _demoDbContext.SaveChanges();
}