Unable to place new sphere after 5000 attempts

Hello everyone!

I'm still learning yade-dem and I am trying to fill a cylinder with a determined type of soil with especific porosity and PSD. For this, I created a cylinder and to fill it up, I tryed to use the CircularFactory engine. Unfortunately, always I run the script the following message appears and nothing happens:

Unable to place new sphere after 5000 attempts

I can't realize where my mistake is.
Please, I would like to know where my mistake is or if there is a better way to fill my cylinder with spheres.
Thanks a lot,

Bruna.

Here is the script:

# -*- coding: utf-8 -*-

O.bodies.append(geom.facetCylinder(center=(0.,0.,0.5), radius=.5, height=1., wallMask=6))
O.bodies.append(utils.sphere((0.,0.,0.05),radius=.05))

O.engines=[
    ForceResetter(),
    InsertionSortCollider([Bo1_Sphere_Aabb(),Bo1_Wall_Aabb(),Bo1_Facet_Aabb()]),
    InteractionLoop(
        [Ig2_Sphere_Sphere_ScGeom(),Ig2_Wall_Sphere_ScGeom(),Ig2_Facet_Sphere_ScGeom()],
        [Ip2_FrictMat_FrictMat_FrictPhys()],
        [Law2_ScGeom_FrictPhys_CundallStrack()]
    ),
    NewtonIntegrator(damping=.2,gravity=(0.,0.,-9.81),label='newton'),
    CircularFactory(center=(0,0,1),radius=.5,massFlowRate=500.,PSDcum=[0.01,0.25,0.40,0.45,0.50,0.55,0.60,1.0],PSDsizes=[0.0075,0.0095,0.019,0.025,0.0375,0.05,0.075,0.1],exactDiam=True,color=(0,0,1),goalMass=1800,vMin=100,vMax=100,vAngle=0,normalVel=(0,0,-1))
]

O.dt=0.5*utils.PWaveTimeStep()