Comparison of the Ca II 8542 Å LOS velocities at different optical depths, using two different inversion strategies with STiC (see Table 1) during the M-class flare (map 2 or panel f) in Fig. 1). Top (A): Restrictions applied to the inversion code. Bottom (B): Solution leaving the code with more freedom. The velocities are clipped between ±6 km s⁻¹. The faint green contours mark the borders of the ribbons as seen in Fig. 1f), using an intensity threshold at I/I_c = 0.87.