Hi,
Good question.
Because of the settings set in the SCR Keydynamics Settings section, then you have a sound using partial 1 in the low end of the keyboard, and a sound using partial 2-4 in the upper end of the keyboard, that have a movement.
If you look in the SCR mixer section, then you see partial 2 and 4 are panned fully right and partial 3 is a little to the left.
Then if you open the extended front panel and select partial 3, then you in the Stereo section can see that the depth for that sligtly left panned partial 3 is set to 100%. That means this partial move in the stereo field according to the Stereo section settings.
The different partial 2-4 pan settings and the Stereo setting for partial 3 result in what i guess you call fade in and out.
If you turn down the depth for partial 3 in the Stereo section, then the movement will go away and you will hear the pan settings set in the Mixer section. That mean you hear a quite right panned sound because of partial 2 and 4s fully right pan settings. Those partial 2,3 and 4 pan settings you then also can adjust to your liking.
I hope that's it.
Just in case. Also be aware the preset use Repeat/ Arpeggio settings. If anyone know if it's possible to only have the Repeat/ Arpeggio on for partials i choose, then i would like to know. In a sound like this somehow to have it on for the sound on the lower part of the keyboard only.
It could be nice if this was possible somehow.
Best
EDIT: I just realized i mentioned a wrong pan setting i have corrected now.