Display of particle trajectories in the presence of parallel worlds

I created a geometry in the parallel world and used the particle source to define I-125. Following the instructions in the manual I entered the command/vis/drawVolume worlds into the program to display the geometry in the parallel world when the program is running. Particle trajectories or even the particles themselves are not displayed in QT, after I removed this command I was able to display the particle trajectories normally. I am using the DICOM example and I would like to ask you all what this might be about.