I've been seeing issues with my surface pro 3 when I try to draw lines. If I make the stroke really fast it looks nice a clean, but if I draw it slowly it looks terrible, all zig zaggy. I know my hands are not that shaky. As an experiment I took a straight edge and used it to draw a series of parallel lines with the pen. Not drawing too fast, more like one second for each line. When I do this I get this weird grid ripple pattern (If you blur your eyes a bit, the grid becomes really apparent). This makes me think there is some issue with the digitizer that is causing a lot of the errors in my lines. I am wondering if this is particular to my hardware or universal. Or if it might be something that just needs a bit of calibration. You can see the pattern I got below. You could try the same experiment with any drawing program that supports the pen. I used sketchbook pro (which doesn't need any additional drivers, and doesn't work right if you install the wintab driver). I was getting similar results with clip studio.