Sweep orientation joined curves - joining curves affecting normals

Hi there I have an issue (which actually has caused me a problem previously…I was previously sweeping along a shallow helix and getting unwanted profile orientation, same issue but a long time ago…)

I am sweeping a profile along a joined curve. The final segment of the joined curve is a planar orthogonal line. The curve normals of this segment are planar with xy. (shown yellow)

However when the curve is joined, the normals at these locations are rotated. (shown blue)

I tried to orient some additional orthogonal profile curves at the beginning and end of this segment, however, my single profile sweep had correctly formed mitered joins between segments which are now broken and i am getting similar problem of misaligned profiles in horizontal parts of the sweep.

Single sweep

Multi profile sweep (also note unwanted rotation of surfaces

I have searched for similar problems and noted most involve a single curve segment and using plane adjust. I worry that adjusting planes locally will produce a kink immediately adjacent to the forced area.

Perhaps a rebuild of this part of the curve and a range of rotations … I will begin to investigate that but feels complex as the planes will be rotating in all axes relative to each other

The curve is part of a wider definition however I had extracted a simple case for help.

Many thanks all

SweepRotationTest.gh (19.7 KB)