Contours describing the χ² surfaces at different black hole masses M_BH and mass to light ratios M/L. Red contours show the χ² surface using the original version of the Schwarzschild code, and were previously presented in den Brok et al. (2021). Blue contours show the χ² surface after correcting the mirroring bug in the code. Grey dots show the locations at which models were calculated. The thick contours contain models within of the best-fit model. The contours do not close for lower-mass black holes and we thus obtain an upper limit. The sphere of influence of a 10⁹ M_⊙ black hole is about 0.05 arcsec which is well below the spatial resolution of the data (seeing FWHM ≈ 0.67 arcsec).