Created attachment 949 [details]
Gif of Bar issue

Using the following code:

        private void InitializeChart(TChart chart)
        {
            void Chart_MouseMove(object sender, MouseEventArgs e)
            {
                for (var i = 0; i < chart.Series.Count; i++)
                {
                    var index = chart.Series[i].Clicked(e.Location);
                    if(index > -1)
                    {
                        chart.Header.Text = $"bar{i}, value:{index}";
                        break;
                    }
                }
            }

            chart.Aspect.View3D = true;
            chart.MouseMove += Chart_MouseMove;


            for (var i = 0; i < 4; i++)
            {
                chart.Series.Add(typeof(Bar)).FillSampleValues();
            }

            ((Bar)chart.Series[0]).MultiBar = MultiBars.Stacked;
        }

You can see that where the Bars overlap there is an issue as to whether the correct value is being returned.