Mean difference in parallax between EDR3 and DR2 as a function of effective wavenumber for several ranges of the G magnitude.Circles connected by solid lines are weighted mean values computed in bins of variable size, with at least 1000 sources per bin, and dashed lines are mean values of the fitted parametrised function ΔZ (Eq. (5)), binned as for the sources. Filled red circles are for sources with β > 0, and open blue circles for β < 0. The vertical dashed lines mark the breakpoints for the basis functions c_j(ν_eff) in Eq. (A.3), i.e. the clamping limits at 1.24 and 1.72 μm⁻¹ and the midpoint at 1.48 μm⁻¹.