Hi Jeff,
Thank you for the answer and for checking on the bug.
The case was running for some days but then it failed. Anyhow, particle segregation was still very aggresive. It may be it is a limitation with the PIC and that collision damping is not behaving as I expected.
I am going to investigate other reactors using MFiX, so I will probably reach you in the future with some other questions. We can close this topic for the moment.
Thanks,
Eduardo