Sweep-1 won’t do. Need Extrude along curve that maintains the starting cross section all along the centerline curve instead of going flat as the extrusion curve turns along the centerline curve and comes back. Its a command and setting, just never use it, and didn’t have it in my written notes.
That gives the same options as the basic command you can get from the menu. I’ve encountered this before, was able to solve once I had the correct command+option, but can’t find it again, now that I need it.