[Bug] Offboard control setpoints affect vehicle when offboard control is not enabled

[fennel-alpineeagle]

Describe the bug

When the offboard control activation command (VEHICLE_CMD_DO_SET_MODE with parameters 1 and 6) is sent to a vehicle with non-matching system ID (as it happens, when the offboard control demo is used in conjunction with multiple simulation instances), offboard control is not enabled. This is a feature and right now I do not consider it as a bug. However, when setpoints are sent in this scenario via the vehicle_command and trajectory_setpoint at the same time, the setpoints do still affect the vehicle behavior, even though offboard control is not activated. Personally, I suspect that something with the setpoint multiplexing for offboard control is wrong.

To Reproduce

Environment: PX4 v1.15 Gazebo SITL @ Ubuntu 22 with ROS Humble, but may work on other configurations.

1. Launch MicroXRCEAgent udp4 -p 8888
2. Launch PX4_SYS_AUTOSTART=4004 PX4_SIM_MODEL=standard_vtol /root/PX4/build/px4_sitl_default/bin/px4 -i 3
3. Take-off
4. Launch ros2 run px4_ros_com offboard_control --ros-args --remap /fmu/in/offboard_control_mode:=/px4_3/fmu/in/offboard_control --remap /fmu/in/vehicle_command:=/px4_3/fmu/in/vehicle_command --remap /fmu/in/trajectory_setpoint:=/px4_3/fmu/in/trajectory_setpoint
5. Observe how the drone starts to jitter in Gazebo, even though Offboard mode is not active according to QGC

Important here: PX4 is started with -i 3.

Expected behavior

The vehicle should fully ignore the offboard setpoints, when offboard control was not properly activated.

Screenshot / Media

No response

Flight Log

Not necessary, as reproducible in sim.

Software Version

PX4 v1.15

Flight controller

n/a

Vehicle type

None

How are the different components wired up (including port information)

No response

Additional context

No response