Sweep 1 rail - bad object with triangle/helix

In the file below, a helix 25 mm radius, 24mm height and pitch 3mm (8 turns). I am sweeping a triangle that has exactly 3mm height around the helix (screw thread cutter).

Seems like this has always worked correctly for me before, but now I am getting a bad object when I sweep it if the triangle height is exactly 3mm. Yes, the edges of each turn touch in this case.

It works without going bad if the triangle height just a tiny bit less than 3mm, but also when it’s a tiny bit more than 3mm… the second one is not bad even if the result overlaps itself.

Hmmm.

Helix-Sweep problem.3dm (118.2 KB)

Hi Mitch - thanks, I see this if Roadlike is used.
Moving the seam in the triangle to the rail ‘helps’…
RH-67623 Sweep1 bad object

-Pascal