Too many Lincs warning

GROMACS version: 2018.1
GROMACS modification: No
I am trying to simulate water and tertiary butanol binary mixture. But in the energy minimization step I found Fatal error: Too many lincs warning (1233) If you know what you are doing you can adjust the lincs warning threshold in your mdp file or set the environment variable GMX_MAXCONSTRWARN to -1, but normally it is better to fix the problem.
My em.mdp file is given below:
; minim.mdp - used as input into grompp to generate em.tpr
; Parameters describing what to do, when to stop and what to save
integrator = steep ; Algorithm (steep = steepest descent minimization)
emtol = 100.0 ; Stop minimization when the maximum force < 1000.0 kJ/mol/nm
emstep = 0.01 ; Minimization step size
nsteps = 10000 ; Maximum number of (minimization) steps to perform

; Parameters describing how to find the neighbors of each atom and how to calculate the interactions
nstlist = 1 ; Frequency to update the neighbor list and long range forces
cutoff-scheme = Verlet ; Buffered neighbor searching
ns_type = grid ; Method to determine neighbor list (simple, grid)
coulombtype = PME ; Treatment of long range electrostatic interactions
rcoulomb = 1.0 ; Short-range electrostatic cut-off
rvdw = 1.0 ; Short-range Van der Waals cut-off
pbc = xyz ; Periodic Boundary Conditions in all 3 dimensions
constraints = allbonds
constraint_algorithm = lincs

I am learning md simulation using Gromacs for last couple of months. It will be very helpful if you could give some input in this regard.
thank you

Quick questions:

What happens if you run just a single butanol molecule? I am wondering if the initial coordinates for your butanol model are the source of your troubles.

Also: why are you restraining all-bonds?

Thank you Mick for your kind concern. Lincs warning is still coming when i run with only teriary butanol molecule. Without restraining the all bonds potential energy has become highly positive after energy minimization. Awaiting for your valuable input.

Your observation suggests an unstable topology. How did you parametrize the molecule?

Thank you jalemkul. All the force field parameter value i have taken from a paper and using those value i have created topology file.