Hello Alex,
This looks like a problem in the component, but there is a relatively simple workaround. You can switch the legend in manual mode and add legend items manually. You can take a look at the following example in our Windows forms demo application:
All Examples > Panels > Legend > General
As for the problem in the auto legend - it will be fixed in the next service pack, which should be available next week.
Best Regards,
Nevron Support Team