Yup .... I did all of that.  Found the start and end points, made sure they were joined ... went all around the problem curves looking for gaps.  These were all on the cross section curves and some other ones I tried to create by joining one hand drawn with a previously close curve.

Anyway, whether it was two ore more curves in the same space, or some pesky unjoined end that I could not for the life of my find, I finally said to hell with it and just moved on.  There is more to life than nitpicking over one or two stupid closed curves that are apparently really open.

Sigh.

Could be worse, could be raining.