Hi Dave,
The issue of the borderline between the two split panes has been confirmed as a defect and our Developers are working on fixing this issue. The fix for this issue is expected to be available on May 30th and we will get back to you on the specified date with more details.
Please refer to the following link for the status update on this defect fix.
http://www.syncfusion.com/support/issues/tools/Default.aspx?ToDo=view&questId=10248Thanks for ypur patience.
Regards,
Janagan.