fix deform issue

Hello Team, Greetings. I'm working on an homogeneous simple shear simulation using "fix Deform" method in LIGGGHTS.

I'm taking a cube of side 3.75 mm filling it with 483 particles each of diameter 500 microns and density 2500 so that the packing / volume fraction is 0.6. There is only 1 atom_type and all six faces are periodic. Particle friction is 0.1 and there is no gravity for time being. I apply "fix deform xy" with a known value of dimensioned shear rate, say 20000/sec, so that the top plane (ymax plane) moves along positive x-direction with a velocity of 37.5 m/s. Script writes out VTK files and I observe that the simulation box / region tilts correctly but the particles do not follow the box. However when I reduce shear rate to 2000/sec, everything works fine. Please see the attached animation with this post. This I have tried with lower shear rates and also for different particle friction values, it works well.

Does anyone know how to fix this issue? Please let me know if you have any additional questions. I can share the scripts if you want more details.

Thank you,
Jagan Mohan.