Spatial profiles (top) and PSF-subtracted spatial profile residuals (bottom) for the [S II]λ6731 line. Transverse cuts each with a width of 1″ (5 pixels) are taken across the PSF and knot/inter-knot regions specified on the plots and the profiles normalised before subtraction. We take the centre (in arcseconds) to be the location of the peak of the PSF, as we are concerned primarily with the relative shifts in knot centroid positions. Note the differences in the knots B and C compared to A and A3, suggesting that the red-shifted jet is less symmetric than its blue-shifted counterpart.