Pencil Tool artefacts - is this a bug?

[Piotr]

Hi, I just got my brand new ArtRage 5. I'm learning everything. I have come across this issue. See image. When I use the pencil tool (not in precise mode) and make a sharp turn in the stroke, some artefacts appear at the corners. Is this a bug or how to fix it? I really like the pencil tool, but with those artefacts it's pretty useless.