Shifts in best-fit values of S​₈ under different residual shear bias scenarios. The shift, ΔS​₈, is calculated as , where represents the best-fit values in the test scenarios determined by a local minimisation method that uses the best-fit values from the fiducial analysis () as a starting point. The grey shaded regions represent different percentiles of the credible intervals derived from our fiducial POLYCHORD run. From the innermost to the outermost region, these percentiles are 6.8%, 20.4%, and 34%, corresponding to 0.1, 0.3, and 0.5 fractions of the reported sampling uncertainties. The dashed lines display the maximum shifts encountered in the six sets of morphology test simulations. These maximum shifts are used as the additional uncertainties in the reported best-fit values to account for the systematic uncertainties arising from shear calibration.