Particle penetrating the wall

Hi all,
I am trying to simulate the single particle falling under gravity.
As a base case I took twoParticleGlowinski case, which uses IB method for particle.
In my case the particle also rotating with certain angular velocity.
the simulation is running fine but when I track the particle position I found that some part of particle is going inside
the wall (i.e. wall normal distance of particle center is less than its radius)

A quick search through forum suggest that it is due to large time step but in my case even with dt=10e-7 same thing is happening

the listing of in.liggghts_run is as follows

echo both
log ../DEM/log.liggghts
thermo_log ../DEM/post/thermo.txt

atom_style granular
atom_modify map array
communicate single vel yes

boundary f f f
newton off

units si
processors 2 2 2

region reg block 0. 1. 0. 1. 0. 4. units box
create_box 1 reg

neighbor 0.03 bin
neigh_modify delay 0 binsize 0.01

# Material properties required for new pair styles

fix m1 all property/global youngsModulus peratomtype 5.e7
fix m2 all property/global poissonsRatio peratomtype 0.45
fix m3 all property/global coefficientRestitution peratomtypepair 1 0.9
fix m4 all property/global coefficientFriction peratomtypepair 1 0.5

# pair style
pair_style gran model hertz tangential history #Hertzian without cohesion
pair_coeff * *

# timestep, gravity
timestep 0.0000001

fix gravi all gravity 9.81 vector 0.0 0.0 -1.0

# walls
fix xwalls1 all wall/gran model hertz tangential history primitive type 1 xplane 0.
fix xwalls2 all wall/gran model hertz tangential history primitive type 1 xplane 1.
fix ywalls1 all wall/gran model hertz tangential history primitive type 1 yplane 0.
fix ywalls2 all wall/gran model hertz tangential history primitive type 1 yplane 1.
fix zwalls1 all wall/gran model hertz tangential history primitive type 1 zplane 0.
fix zwalls2 all wall/gran model hertz tangential history primitive type 1 zplane 4.

# cfd coupling
fix cfd all couple/cfd couple_every 100 mpi
fix cfd2 all couple/cfd/force

# create single partciles
create_atoms 1 single .5 .5 3.5 units box
set atom 1 diameter 0.2 density 1500 vx 0 vy 0 vz 0 omegay 4

variable vx1 equal vx[1]
variable vy1 equal vy[1]
variable vz1 equal vz[1]
variable x1 equal x[1]
variable y1 equal y[1]
variable z1 equal z[1]
variable omegax1 equal omegax[1]
variable omegay1 equal omegay[1]
variable omegaz1 equal omegaz[1]
variable time equal step*dt

fix extra1 all print 100 "${time} ${vx1} ${vy1} ${vz1}" file ../DEM/post/velocity_particle_1.txt title "%" screen no
fix extra2 all print 100 "${time} ${x1} ${y1} ${z1}" file ../DEM/post/position_particle_1.txt title "%" screen no
fix extra3 all print 100 "${time} ${omegax1} ${omegay1} ${omegaz1}" file ../DEM/post/angular_velocity_particle_1.txt title "%" screen no

# apply nve integration to all particles that are inserted as single particles
fix integr all nve/sphere #wenn das ausgeblendet, dann kein vel update

# screen output
compute rke all erotate/sphere
thermo_style custom step atoms ke c_rke vol
thermo 1000
thermo_modify lost ignore norm no
compute_modify thermo_temp dynamic yes

# insert the first particles so that dump is not empty
dump dmp all custom 100 ../DEM/post/dump.liggghts_run id type x y z ix iy iz vx vy vz fx fy fz omegax omegay omegaz radius

#force : f_couple_cfd[0] f_couple_cfd[1] f_couple_cfd[2]
#node : f_couple_cfd[6]
#cell id : f_couple_cfd[7]

run 1

Any help in this regards will be highly appreciated

Atul M. Bhagat