Energy Minimisation error

GROMACS version: version 2020.1-Ubuntu-2020.1-1
GROMACS modification: No

Hello Everyone,
I’m trying to do energy minimisation for my system which contains a protein (441 residues), 25 Cu2+ ions, 52 Cl- ions and 10 molecules (phenylindane). solvent is water.

I’m getting the error of,
Energy minimization has stopped, but the forces have not converged to the
requested precision Fmax < 10 (which may not be possible for your system). It
stopped because the algorithm tried to make a new step whose size was too
small, or there was no change in the energy since last step. Either way, we
regard the minimization as converged to within the available machine
precision, given your starting configuration and EM parameters.

Double precision normally gives you higher accuracy, but this is often not
needed for preparing to run molecular dynamics.
You might need to increase your constraint accuracy, or turn
off constraints altogether (set constraints = none in mdp file)

writing lowest energy coordinates.

Steepest Descents converged to machine precision in 78 steps,
but did not reach the requested Fmax < 10.
Potential Energy = 4.4149275e+06
Maximum force = 2.2788421e+08 on atom 2405
Norm of force = 4.2649535e+05

I have read previous solutions for this error and did everything as they suggested in here,

my .mdp parameters are,

ntegrator = steep ; Algorithm (steep = steepest descent minimization)
dt = 0.002 ; Energy step size
nsteps = 1000

continuation = no
constraints = none

cutoff-scheme = Verlet

tcoupl = Berendsen
tc-grps = Protein Cu Cl US5F SOL
tau-t = 0.1 0.1 0.1 0.1 0.1
ref-t = 300.0 300.0 300.0 300.0 300.0

pcoupl = Berendsen
tau-p = 0.5
compressibility = 4.5e-5
ref-p = 1.0