Seams Mystery

These tubes all started out the same - extruded or swept circles.
Some have been subtly point-edited. I need none of them to display seams , but I can’t get rid of the display of seams on several of them. I don’t understand how to control this. The file is attached below.

InconsistenSeamDisplay.3dm (419.3 KB)

Hello - not subtley enough, I guess.

Your editing has made them into polysurfaces - if a true NURBS circle or cylider is point edited such that the points are out of line across the quadrants, then a kink is created and surfaces break into polysurfaces. The solition is to Rebuild the circles before extruding/sweeping, or RebuildUV the surfaces after.