I have tried, but I could not reproduce the effect.
Probably stupid question, but... Have you ever used "Remove control..."? Right click on the fader which is jumping to 0, and select "Disable remote control", if it is enabled (so you have used it). I am asking since Knobs are sending normal CC messages and the value when you turn it right is 1-3 (almost 0 since the max is 127).
Also check the fader is not "grouped" with something.
Since you have not mentioned your audio interface, if it is "smart" one (RME, X32, etc.) please check that you are not routing MCU to it (at least not when controlling Sonar).
Otherwise lets narrow when that happens: how many tracks your projects have (where that happens and where that does not happened)? MIDI, Audio, Instrument (Especially the track 5)? When that happens in the Track mode, do you see "TR" or "TR." (with dot) on small display? What strip 4 display is showing?
What is jumping, your audio interface output or Master bus (that is the setting in the plug-in preferences)? Try to change it, so set to "Master" if it was "Bus" and set to "Bus" if it was Master. Is jumping parameter different then?
Are you using any external MIDI loopbacks/translators?