Ok something is definately bugged.
I have a painting where the only medium is Chalk.
Then i use the Palette Knife to blend colour, but almost nothing happens no matter how I set the Pressure.
But then i can hit a small area of the picture where the Palette Knife turns the Chalk into Oil Paint.

I didn't use Oil Paint at all so this is just what the Palette Knife tool is doing.

I was using ArtRage5 but i have uninstalled it, installed ArtRage6 and the behavior is the same.
How is that possible?