For whatever reason, standing animations and sitting animations do not follow the same spotting positions. So when you do the stand to sit transition, your character is in a “standing” spot position. When you follow it with a sitting animation, the spot positioning will change to a “sitting” spot position.
In my experience it’s a bit difficult to direct this because you have to use trial and error to get the positions to match. If you try this, you’ll have to add a spot positioning command to the sitting animation.
If you can, I’d suggest zooming in this character, a different one, or panning across a different zone while you have the character do a sitting animation. That way you don’t have to make the positions match perfectly, and you avoid the awkward shifting you’re talking about.