"keep" in OffsetCurve filter does not result

I have always successfully used keep in the OffsetCurve export filter to avoid distortions caused by negative space in narrow corners.

OffsetCurve; 10; 10; auto; keep;

It does not seem to work anymore. The result contains the same distortions as without the keep.

A zero was missing.
It has to be:
OffsetCurve; 10; 10; 0; auto; keep;

The keep option is there to make it not add points (as it would sometimes to improve the results). So I would expect more distortion if you add that parameter.

See the example above what happens if I do not add the keep.
But I figured out my mistake, thank you!

Can you send me an example file?