We studied the effect of non-hydrostatic pressure on the hysteretic spin crossover in coordination complexes. By introducing into an Ising-like model a double distribution of the interactions and gap energy, respectively, we were able to generate the major hysteresis loop and the first-order reversal curve (FORC) diagram for spin-crossover systems of 106 hysterons (like-spin domains). We show that, for high pressure gradients around the spin-crossover system, the thermal hysteresis loop takes an asymmetric shape, in good agreement with the experimental data on pressure effect recorded at low temperatures, below the solidification of the pressure transmitting medium. Interestingly, the FORC diagram method seems to be much more sensitive to local changes than the "bulk"parameters, which characterize the major hysteresis loop.