Any time I try to loft more than 2 of the rectangles in the attachment:



using a straight style loft, it creates the artifacting seen in the attachment:



And the loft checkbox to create a closed loft appears (checking it makes a different, but equally bad artifact seemingly skipping over a profile). If I loft these rects 2 at a time and then union the results I get exactly what I want.

I'm using v3 nov 19.