Core position as a function of frequency for the two different data sets: i) the multi-frequency VLBA data set (orange points) and ii) the multi-frequency and multi-epoch data set presented in Boccardi et al. (2021) (blue points). The blue line represents the best-fit values presented in Boccardi et al. (2021), the orange line traces the best-fit performed in this paper by employing all the data, and the purple line highlights the best-fit curve obtained using only the data points at 8, 15, 22, and 43 GHz.