Preflight check fail - altitude error for multiple drones

I have tried multiple drone simulation and I started with 4 drones. I follower this Multi-Vehicle Simulation with Gazebo | PX4 User Guide and I have an issue with 2 of those 4 drones. They cannot be armed and they give me a message about preflight fail high estimate error. I dont know why. 2 drones work just fine, but 2 are aleays with this message and it seems to be random.
Does anyone have any idea how to fix this? Pls…