Problem: dense packing under gravity will not be formed even the particle velocities are nearly zero.
Conditions: insert particles more than a critical number.
tested versions 2.0.4, 2.1.1
I think this should be a bug where the gravity field is lost when the total particle number is larger than a critical value (I am doing test and will tell the critical value in the following given case).
Files attached: geometry (cubic.stl, extension has to be changed), input (in.packing, extension as well), and a result using liggghts 2.0.4.