Evolution of polarization fraction (top), flux density (middle), and position (bottom) of the VLBA components as a function of time. We adopt a flux measurement uncertainty of 10%, which is typical for VLBA data, and the position error is estimated to be one fifth of the fitted Gaussian size. As the polarized intensity images in MJD 57235 and 57287 have a higher noise level (see Sect. 2.5), a polarization fraction could not be derived for all components in these epochs.