Why these artifacts?

What are the strange artifacts in the lower shape? I created both pieces using the same profile. The top is just extruded, the bottom is a sweep1.

booleanunion, or possibly sweep it in one go?

FYI, the straight part and the hexagon are not joined. I included it as an example of the correct finish. I can’t believe sweep1 cannot be used on a hexagon curve correctly. I eventually built the shape out of straight parts and trimmed. Then exploded to trim more and rejoined. A whole lot of work. Will I have to abandon hexagons as a shape?

Hello - please try setting the render meshes in DocumentProperties >Mesh page to ‘Smooth and Slower’ if it is not already. Does that change anything?

-Pascal

Pascal, that was the setting. I solved the construction another way and have moved on. But it still bothers me. If it happens again I’ll save the objects and try to sort it again.