Potential Energy of the system always zero while deforming the box

Hi

## version 3.3.0

I am running this code, which inserts two layers made of two sets of random generated packings.
Since I need to compress the volume in order to reach a relatively high volume fraction (higher than 0.8), I apply an isotropic compression to the box, reducing its final dimension.

The problem I have is that the potential energy of the system during compression and relax, is always zero, while the kinetic energy has quite reasonable values.

These are the related commands I have used:
http://www.cfdem.com/media/DEM/docu/compute_pe.html
http://www.cfdem.com/media/DEM/docu/compute_pe_atom.html

Could anyone have a look and suggest me what could be wrong in my code?

Hereby I attach the code: I have tried to relax the packing for different times so I built different simulations.
I suggest to start from the file named

Local_Tension_Swelling_Prova_duemuri_relax50000

Greetings,
Luca