FDuplicateDataWriter don't copy all object data

I’m trying to create custom spline (camera spline). I already create visualizer and now adding additional data to my spline ( UPROPERTY() FInterpCurveVector SplineDirectionInfo;).
I recently find that when I edit my spline, editor is coping it and replace it whit his copy but SplineDirectionInfo is not copied.

I hate to bumping but I really need help with this. I spend many hours and can’t understand how objects are copied.