What version of Revit are you using as in previous version if the data could not be written/sorted it was blank and it looks like some of these row may relate to missing information?
In newer version you get the message <varies> so you may need another level of sorting!
Also in the Sorting Tab there is an option for Blank Line as well as the formatting Tab
Jay Colcombe
Autodesk Certified Instructor
Revit Architecture & Structure Certified Professional
AutoCAD Certified Professional
B.Sc. Hons Civil & Structural Engineering
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