Orbital models and planet astrometry. Top: November 1, 2019 epoch astrometry overlaid as gray diamonds on the most dynamically stable orbital solutions from Wang et al. (2018; see their Fig. 4), where coplanarity and 1:2:4:8 period commensurabilities were imposed. The black dots represent earlier measured astrometry for the four planets. Bottom: Same points overlaid on the orbital solutions without the additional constraints. The 2019 locations for planets e and c are more consistent with the dynamically stable family of orbits.