I took a look at the file. The spoke curves are "pre-cornered" or rounded.. Any type of blend will be "lumpy". I put an arc on it and swept it along the 2 paths, and it created the same lumpy output.. (Lumpy meaning, there was a smooth blend or arc fillet, but it's height changed as it swept around)

I think you may need to change the input curve to be hard edges, then fillet after, or even to seperate pieces for each angle direction, then put them together later....