Thanks for the template file and screenshots.
Please notice, I am able to reproduce the issue as you mentioned by rendering the chart in the worksheet to image format. I found some chart legend items are cut off in the output image:
Workbook workbook = new Workbook("f:\\files\\test-chart.xlsx");
WorksheetCollection ws = workbook.getWorksheets();
Chart chart = ws.get("sheet").getCharts().get(0);
ImageOrPrintOptions imgOptions = new ImageOrPrintOptions();
I have logged a ticket with an id “CELLSJAVA-45008” for your issue. We will look into it soon.
Once we have an update on it, we will let you know.