Pair_Brownian: dynamic viscosity inceasing cause huge increase of temperature

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Hi dear whom it may concern
I am doing a coarse-grained model of diffusion of nanoparticles in fluid. I use Bronian style with nvt and langevin. The problem is that when I increase the dynamic viscosity(DV) in pair_brownian command, the temperature increase greatly, much more than what I set via fix command.
Blow is my script:

units nano
atom_style sphere
dimension 3
boundary p p p
newton off

lattice sc 10
#lattice command defines the type of box, sc means simple cube, the number after sc is scale factor. For units lj, the length of box cubed times scale factor euqal to 1.
region box block 0 48 0 48 0 48 units lattice
region case block 19 28 19 28 19 28 units lattice

create_box 1 box
create_atoms 1 random 1000 20190714 case

set atom 1 diameter 5
set atom 1 density 0.0015

neighbor 10 bin
neigh_modify every 1 delay 0 check yes page 10000 one 1000

pair_style brownian/poly 0 0 1 5 10 310 20200514
pair_coeff * *

compute rot all temp/sphere
compute kte all ke
compute pec all pe
compute pre all pressure rot
compute kre all erotate/sphere
compute angularvelocity all property/atom omegax omegay omegaz
compute shape all property/atom radius diameter
compute Temperature all temp

velocity all create 298 20200525 dist gaussian loop geom
run 0
velocity all scale 298.0

variable step equal step
variable pe equal pe
variable ke equal ke
variable Total_energy equal etotal
variable Pressure equal press
variable Volume equal vol
variable Temperature equal temp

#calculate diffusion coefficient
compute 2 all vacf
fix 5 all vector 1 c_2[1]
variable Diff equal dt*trap(f_5)

timestep 0.002

fix 2 all print 2000 “{step} {pe} {ke} {Total_energy} {Pressure} {Volume} {Temperature} {Diff}” file test.txt screen yes
dump 2 all custom 2000 0731.dump id type x y z

fix 1 all nvt temp 310 310 50 drag 1

thermo_style custom step pe ke etotal press vol temp v_Diff
thermo_modify lost ignore

run 3000000

when I change pair_style brownian/poly 0 0 0 5 10 310 20200514 to pair_style brownian/poly 1 0 0 5 10 310 20200514,
the temperature increase from 310K (which is desired) to over 60000K,
How should I do to make the temp stay at 310K with changing the DV?
and tbh when I include Fast Lubrication Dynamics effects, the temperature change from 1000K to about 550K, why does that happen?

Thanks in advance!! Looking for your reply!