Check and Download updated mission.

[KonradRudin]

Mavlink and PX4 introduced the Opaque ID for the mission/geofence/rally. https://github.com/mavlink/mavlink/pull/2012 https://github.com/PX4/PX4-Autopilot/pull/21839

Now, an uploaded mission is assigned an ID on the MAV and send down on the final ack of the uploaded mission. Further the active mission/geofence/rally ID is continuously streamed down in the MISSION_CURRENT mavlink message. With this information the QGC can infer, if a mission has been changed onboard and reload the mission if the currently displayed mission is different. This is helpful if the mission has been changed either by a different QGS instance or by a companion computer.