4. Variability in freezing behavior: For the engineering run at -40°C, vials close to the exterior cool down faster than their inner counterparts, and reach low temperatures already at times when core vials are still at the stationary temperature. At -20°C, all vials exhibited similar thermal evolution profiles, while for -25°C minor differences between the readouts were observed. Regarding the simulations, we find that the side vial nucleates generally earlier than the core vial and with less variability in time. We analyze variability in freezing behavior among vials in section 3.6, based not only on the thermal evolution profiles, but also on the nucleation and solidification behavior; this analysis reveals that significant variability is present at all storage temperatures, with potential impact on drug stability.