Thanks for the feedback. I checked and the SP2 has a 1920x1080 display, so I can imagine that you don't have Windows 8 scale the display. You find it via rightclick on the desktop and choosing "Screen resolution". Then in the Screen Resolution window choose "Make text and other items larger or smaller". If you have 100% (and from I read even 125% would be fine) there, you probably won't notice anything. At least that's one workaround that Ableton suggested, and I saw something similar for a videogame that had the same issue.
If you put scaling to 150% or higher, then the jumping occurs, because the software just sees a small move as being a move of quite a lot of pixels and thus moves the fader up/down way more than what your true movement is.
EDIT: after typing this, I realized I could try the Ableton tip of using 100% scaling. But it turns out that it does not help at all, not even with Ableton Live. So the above explanation doesn't make sense either. Basically I have no idea why faders behave like that in both Ableton Live and Sonar X1.