Need to get point index value when custom range selectors are made

General
1 
    Hello,
    
    I have made my range selector buttons to custom for 1 minute, 10 minutes, 1 hour, 1 day and all as shown in the below code.  All these buttons are working great. 
    But, when I am trying to get the point index value from the graph, I am getting point index as -1 when I set my range to 10m, 1hr, 1 day and All. 
    I am getting the exact point index value when I set the range to 1 minute. I don't have any idea why I am able to get point index value for 1-minute range and why am I not able to get point index value for other ranges? I don't know if I am missing something. 
    Please, help me with this and I have pasted the code which I am using to get the point index value from the graph. 
    By the way, vaadin version I am using is vaadin version - 8.0.1 and vaadin charts version - 4.0.0. 
    When I click on the graph I want to get the exact point index value in all the ranges... Please, someone, help me with this...  
    
    
    RangeSelector rangeSelector = new RangeSelector();
    RangeSelectorButton button1 = new RangeSelectorButton(RangeSelectorTimespan.MINUTE, 1, "1m");
    RangeSelectorButton button2 = new RangeSelectorButton(RangeSelectorTimespan.MINUTE, 10, "10m");
    RangeSelectorButton button3 = new RangeSelectorButton(RangeSelectorTimespan.MINUTE, 60, "1h");
    RangeSelectorButton button4 = new RangeSelectorButton(RangeSelectorTimespan.DAY, 1, "1d");
    RangeSelectorButton buttonAll = new RangeSelectorButton(RangeSelectorTimespan.ALL, "All");
    rangeSelector.setButtons(button1,button2,button3,button4,buttonAll);
  
  
    rangeSelector.setSelected(4);
    configuration.setRangeSelector(rangeSelector);
    
    List<Series> seriesList = getConfiguration().getSeries();
    DataSeries totalSeries = (DataSeries) seriesList.get(0);
    DataSeries flagSeries = (DataSeries) seriesList.get(flagSeriesIndex);
    Number flagLocation = (totalSeries.size() > 0) ? totalSeries.get(index).getX() : 0;
    flagItem = new FlagItem(flagLocation, "V");
    flagSeries.add(flagItem);
    
    
     this.addPointClickListener(new PointClickListener()
    {
        @Override
        public void onClick(PointClickEvent event)
        {
           int selectedPointIndex = event.getPointIndex();
           System.out.println("Selected index  "+selectedPointIndex);
           currentTimeSeconds = selectedPointIndex;
           updateFlagPosition();
        }
    });