Hello, there are times when the drone performs random and unprogrammed behaviors, such as going to unordered positions, taking off from the water, crashing into the sea, or getting lost over the horizon. This makes it quite difficult to schedule and carry out the practice.
PX4 autopilot + mavROS + ROS1 Noetic is sometimes unstable when running on Gazebo, and it often shows unexpected behavior. Just try several times. Running it in a powerful computer or alone with no other concurrent applications helps.
In addition, you could try with newest release of PX4 autopilot + ROS2 Humble + Aerostack2, which is available at RADI 4.4.19. and later releases.