To reproduce:

Add a RadChartView and setup drilldown. Add a RadRangeSelector and associate the chart with it. Start the application and drill down, you will see that the layout of the chart is not updated accordingly.

Workaround:

In the Drill event handler save a value whether a drill has occured. On the MouseUp event of RadChartView update the layout of the chart:

private bool drill;
void Chart_Drill(object sender, DrillEventArgs e)
{
    drill = true;
}

void Chart_MouseUp(object sender, MouseEventArgs e)
{
    if (this.drill)
    {
        Application.DoEvents();
        (this.rangeSelector.RangeSelectorElement.AssociatedElement as IRangeSelectorElement).UpdateAssociatedView();
    }

    drill = false;
}