Multi-vehicle simulation with Gazebo and ROS 2

I am attempting to takeoff multiple iris vehicles in Gazebo using PX4 and ROS 2. I am using mostly the instructions from the first part of this doc (i.e. starting Gazebo through the bash script, then start an micrortps_agent for each vehicle). Then, I am also running an offboard_control node for each iris (based off the script in this tutorial), which sets offboard mode, arms the vehicle, and commands it to takeoff. I made another bash script to automate running all these commands. However, I noticed that with multiple drones, the drones do not always all take off. The first drone usually consistently takes off but often times the others do not (success rate seems to decline with more drones). It is also not consistent between runs which drones take off. When running the script, I noticed all the drones take off, drones 1 and 3 take off, drones 1 and 2 take off, etc. I was wondering if anyone else has attempted this. I could not find any documentation about Multi-vehicle with Gazebo and ROS 2.