Michael,
reducing the number of turns appears to reduce the amplitude of the sawthooth pattern but it does not remove it by any means. Turning the curves over on their sides does fix the problem (regardless of the number of turns). I have included the file just in case you still want it...thanks for the help.

possum

Thanks for the file possum - there definitely looks like a bug there to track down.

In the meantime it does appear that if you keep both curves to be within the world x/y plane instead of going in a vertical direction it should work better.

- Michael