Steps to reproduce:
1. Add a pie series to a chart 
2. add three data points with values 19,20 and 61
3. Set the series LabelsOffsetFromCenter property to 0.2d
4. Run the project and start reducing the size of the chart. At some point you will see that the position of the label 20% will be incorrect.

Second scenario:
Add a pie chart and populate it with PieDataPoints, one of which is with value 0:

        Me.RadChartView1.AreaType = ChartAreaType.Pie
        Dim series As New PieSeries()
        series.DataPoints.Add(New PieDataPoint(50, "Germany"))
        series.DataPoints.Add(New PieDataPoint(70, "United States"))
        series.DataPoints.Add(New PieDataPoint(40, "France"))
        series.DataPoints.Add(New PieDataPoint(25, "United Kingdom"))
        series.DataPoints.Add(New PieDataPoint(0, "Italy"))
        series.ShowLabels = True
        Me.RadChartView1.Series.Add(series)