Tracking the movement of particles through the domain can lead to an incomplete fate. A usual remedy is to increase the “Max. Number of Steps” in Tracking Parameters of DPM setup to follow the particles for a longer distance. If this does not change the fate of the particles, a deeper look at the particle velocities may explain why an increase of integration steps would not help. If, for example, the relative velocity between the mill walls of a stirrer and the particles is almost zero, the fate of these particles will remain incomplete. Another possible reason is that the particles are stuck in the recirculation zone.