Hi Michael,
Thanks a lot for your interests in Syncfusion products. We are not able to reproduce the issue since we have fixed this issue and well tested before the release(6.3.0.25). We suspect the problem might be with the assemblies packed in your system. Could you please uninstall and reinstall properly. Kindly ensure that all the assemblies are packed both in GAC as well as in the reference assemblies folder.
For your reference we have created a sample as per your requirement. Kindly download the sample from the below mentioned location and try to reproduce your issue in this sample.
http://www.syncfusion.com/Product/uploads/GroupBar_16249a6d.zipStill If you are able to reproduce the issue. Please remove all the assemblies manually from GAC and Referenced assemblies folder, then try to reinstall.
Please let us know if you have any queries.
Regards,
Bala Vasanth.