Steps to reproduce.

1. Add a chart view to a form.
2. Create a series and add several data points. For categories use double values in the range 10 - 20
3. Create a second series and this time for categories use double values in the same range without duplication.
4. Assign one linear and one categorical axis to the series and add them to the char view.
5. Run the project and you will see that the categories from the second series are next to those from the first series, while they should be combined according their values.