Evolution of the spectral index between 22 and 43 GHz along the deprojected distance from the SMBH. Weighted mean values across the jet are used in this distribution (see Sect. 3.2). The projected distance is displayed on the upper axis in mas, and the corresponding deprojected distance is displayed on the lower axis in r_s. Red lines represent the spectral index distribution from 2016 KaVA observations and blue lines the spectral index distribution from VLBA observations from 2010 and 2014. The shaded area is the 1σ error of the spectral index.