Notes. The positional matching errors are discussed at the end of Sect. 2.1 and the positional matching of knots between the two WCS matched data sets was done by matching knot shapes and centroids with consideration of their expected motion in the plane of the sky. Given that additional positional matching errors may arise from flux variations along a single knot between the two epochs (see S12, Fig. 10) or misidentification of a knot, average errors are of the order of ±1′′ and maximum errors are expected to be up to 3′′. The errors in the radial velocity are of the order of ±22 km s^-1. As the MES wavelength range does not fully cover the three [N ii] 6548Å, Hα 6563Å, and [N ii] 6583Å emission lines, the following measurements were done with the [N ii] 6583Å where possible, and the [N ii] 6548Å elsewhere; the Hα 6563Å line velocities were also measured as a sanity check.