Pressure not getting equilibrated to desired value

I am doing simulation of alumina atoms. I want to get the desired temp of 300 K and 1 bar pressure.

Temperature is reaching the desired value of 300 K but pressure is sometimes very positive (2000 bar) or sometimes too negative (-3000 bar) I tried with different Pdamp values of 10, 100 but not getting the required pressure.

timestep 0.005 # picoseconds
velocity all create 300 102486 mom yes rot yes dist gaussian

fix 1 all npt temp 300 300 1.0 iso 1.0 1.0 10.0
run 30000

Are those mean pressure that you’re reporting? Because pressure can wildly fluctuate, specially in an incompressible system.

Also take a look at this thread where Axel has clearly explained the reasons.