Time dependence of the DM offset from the total potential minimum in Eris (blue) and ErisDark (red). The gravitational softening _soft( z) = 124 pc is indicated with a dashed line. In ErisDark the DM offset remains around or below 1 _soft for almost the entire simulation, while in Eris it begins to significantly exceed _soft around z = 1.5 and remains at ≈3 _soft afterward.