There is often a slight decrease in the N term peak, likely where the N term domains join the trimers at the center of the dodecamer. This is an infrequent event and its detection is also related to how one draws the plot line through the center of the image of the molecule.  When the N term peak width is listed there are occasions when it interferes (reduces) the total N term peak width. The tiny change in grayscale (height and valley) of the N term peak is pretty small. I have put a ? in the title of this peak to denote its inconsistent appearance.

It is nevertheless listed here in a graphic and below, it appears in two of the eight trimers in these data.