According to the image you have shared, it seems like the order of your categories is different than the one used for the first series which have more data points than the other. If this is correct, could you try rearrange the order of your data points so it matches the one used in the other series. Also, are you using different ItemsSource for each series or it is the same for both.
I have prepared and attached a sample example demonstrating a scenario similar to yours. Could you update it or send us a sample of yours reproducing the issue so we could provide you with a better solution in case the one above does not work for you. Please note that this is a forum thread and you should use a third party web site for files upload and sharing or you could simply log a support ticket and attach the sample there.
the Telerik team