Paintbrush paints noisy strokes at low sizes

[cactushead]

Thanks for your advice. I realise now that I gave a misleading picture of my brush settings because I changed them between drawing the strokes and taking the screenshot.

Here's a picture that represents the settings I used.

   

I've deleted the devicerc file and changed dynamics to 'Dynamics Off' as you suggested, but I'm still seeing the behaviour. The smoother diagonal stroke at the bottom was drawn with 'Smooth stroke' turned on, quality 100 and weight around 500.