BroadNibber problem creating true shape

I am using the BroadNibber Filter to run along a simple curve. It behaves funny and I don’t know, what I do wrong. Here is an illustration to my problem:

Did anybody have this problem before? What do I need to change?

Thanks in advance,

The contrast is probably too much for expanding this curve.

I tried it with less contrast, and it works better. But what should I do, if I need that much contrast? Is there any other way to do this kind of automation?

It has to do with the way the parallel path is calculated. You may try rewiring your path, like more or fewer nodes, different handle distribution, etc.