The solution for this is to use the precise pencil. Click the toggle beneath 'precise' in the left hand tool settings panel to turn this on. ArtRage normally uses a rendered stroke path for most of its tools. This has advantages for things like brush bristling, paper interaction and so on, but when you're doing stroke reversals like in your screenshots, ArtRage has to make assumptions on the rotation of the tool.
Using precise pencil mode makes ArtRage use a method similar to a number of other art applications and shouldn't exhibit this particular behavior.