The Area series values aren’t updated if property smoothed is enable.  The code below shows the problem:
  public Form1()
        {
            InitializeComponent();
            InitializeChart();
        }
        Steema.TeeChart.Styles.Area area1; 
        private void InitializeChart()
        {
            area1 = new Steema.TeeChart.Styles.Area(tChart1.Chart);
            area1.FillSampleValues();
            area1.Smoothed = true;
        }

        private void button1_Click(object sender, EventArgs e)
        {
            area1.Clear();
            area1.FillSampleValues();
        }