I've tested all craft, they are all doing it. Lets just say SLS with Orion then. The change can change the periapsis (from apoapsis) or apoapsis (from periapsis) by 200- 400 meters when in LKO. Now lets say I have a Duna encounter, with a periapsis, but I'm still in Kerbol's sphere of influence. When moving around then, it will change the periapsis by 10- 20 Km.