Desalination simulation

GROMACS version: 2021.2
GROMACS modification: Yes/No

Dear Experts,

I am a beginner in materials simulation, trying to simulate desalination through MOS2 layer. I am attempting pulling simulations using distance as CV, above layer has been used as a piston. With the pore size of 1 nm, my system gets crashed after 38 ps.Movie
script

pull_npt.mdp (3.6 KB)

After using the script attached I am able to see piston movement. I wanted to perform simulation at different pressures as reported in literature. I tried changing the ref_p value to 20, 50, 100, 500 and performed independent simulation with no significant change in the filtered water molecules count. However when increases the “pull_coord1_k = 2500000” water count changes significantly.
But I can’t quantify the amount of pressure applied on the piston as it is increasing rapidly. Please help me in solving the problem.