Hi.
I have founded, that in new version (i have used 8.5.1, but issue appears earlier)
If i will try to set first series of copied chart to second Y axis, then
i will catch exception.
@Test
public void chartSecondaryAxis() throws Exception {
Workbook wb = new Workbook("D://chart.xlsx");
Worksheet worksheet = wb.getWorksheets().get(0);
ChartShape chartShape = worksheet.getCharts().get("Chart1").getChartObject();
Shape copyShape = worksheet.getShapes().addCopy(chartShape, 19, 0, 2, 0);
Chart copyChart = worksheet.getCharts().get(copyShape.getName());
copyChart.getNSeries().get(0).setPlotOnSecondAxis(true);
wb.save("D://out.xlsx");
}