Well, in a few days it’s going to be a new year, 2018 and the MCU protocol is still one of the only control protocols available to have some hardware control, so I’ve just switched from an Artist Mix (a largely overvalued plastic box with faders) to a Behringer XTouch and I can’t believe to see the faders jumping noisily between values. It happened to my old Mackies 15 years ago!! I know it’s a problem with Cubase, because it does not happens with Studio One. And the fix is easy: just send more values.
I hope Steinberg could fix it eventually. Sadly, we don’t have too many options these days to control Cubase but MCU/HUI (pretty much the same), EUCON (overvalued controllers) or Nuage (same as EUCON).
I have an XTouch sitting on a shelf as I’m going to sell it, having replaced it with a new Mackie MCU. I encountered the symptoms you describe with both, found the problem and fixed it. I don’t know if it’s relevant to your setup or not but thought I’d offer the info.
Prior to going the XTouch / MCU route, I had Steinberg’s CMC controllers, which I liked very much. I only made the switch because I wanted physical faders. However, when I set up the new XTouch / MCU in the control room, I left my CMCs connected in the live room so that I had remote transport control, etc.
Two of those controllers were the Faders unit and a Channel unit, which also had a fader. I discovered that the CMC faders were also communicating with Cubase and fighting for control. So, periodically, I’d get random large jumps in fader position on the XTouch/MCU. I removed the fader oriented CMCs and the problem immediately went away. I haven’t seen those symptoms at all from that point on.
I would suggest that you review your entire MIDI setup, i.e. every single device that’s talking to Cubase, whether it’s actually a control surface or not. If any device is transmitting on the same CC / etc. that your XTouch uses, you’ll have exactly the problem you’ve described.