You'll probably do better if you post a sample so folks can test exactly what you're seeing
Works fine for me with our sample data set:
I'd suggest you make sure you're running the latest version of 8 (which is 8.4) and then submit a case to tech support if you're still seeing the issue with your dataset. While a screenshot is helpful, it would be better if you post your workbook here so someone can work with the exact same thing you are. If you can't post it here, you might feel more comfortable sending it to tech support.