Multicopter almost fly away

Assalamualaikum and Good Day.

It is a calm day in the afternoon, when our 1st customer fly their drone. It is a 1100 mm size drone, pixhawk cube orange, with dual here3 gps, two lidar sensor for forward obstacle avoidance and down obstacle sensor and Herelink RC control. It fly with two payloads, one of the payload is a chinese made camera, powered with 12v BEC and controlled by another remote controller (flysky i6) and another loud speaker that is have its own internal battery. (magnetic interference is considered safe). 1 single 6S battery with 22000 mah is used for the drone. Everything is fine when we tested and deliver.

The story from our customer starts…

The first flight in the morning, is fine, the drone take off with Loiter Mode, go to 2 positions, and then switch to RTL. Then they take off the battery, and have some rest before the next flight.

On second flight, they turn on the drone, and start to upload mission waypoints using herelink controller. The mission is keep simple, Take off- go to waypoint 1 - hold 10 secs - go to waypoint 2 - hold 10 secs - then RTL. Geo fences is also set around the mission area and inclusion is checked.

As usual, they start to slide the confirmation button for the autonomous mode, the drone is then take off- fly to waypoint 1- holding for 10 secs - fly to waypoint 2 - holding for 10 secs and RTL.

The drone arrived at Home point, yaw as it should, and at this point it should start to descent. The current altitude is at 40 meters. Suddenly, the drone Roll to the right by itself and speeds as stabilize flight mode. The operator aware of this, and just let the drone to fly until it reached the geofence. But, the drone did not invoke at geofence and passed the geofence.

They aware of this, and then they click Loiter Flight Mode, but the drone got no response, still maintain its speed and its direction. Next, the operator click RTL button. The drone brakes, (recorded 60 degress of roll in flight log) and come back towards RTL point. It is a relief right! But not yet…

Once the drone reached RTL point, and align by yawing as with the take off position, the drone starts doing the previous action. Roll to the right, and fast. Loiter is clicked but no response. Only RTL responded after the operator clicked. The drone return to RTL, but no landing. Once it reach the RTL point, it starts to repeat the previous actions.

Until around 20 times, the drone finally on its way RTL, it stopped, and do auto landing, in which we agreed that the 2nd low voltage kicks in in which auto landing invoke.

End of the story.

When we checked the log, I cant find the issue. Please help me to shade some light.

Normal Flight: https://drive.google.com/file/d/19l3181cOLLwv4OtBJynzKC4Ih1qE0FLX/view?usp=sharing

Almost fly away flight: https://drive.google.com/file/d/1NzUzK1-wvLYMiVNRIkx5CDN0IyLZV965/view?usp=sharing

Yes. Thank you.

Do you know what is the cause of this? we use Herelink controller.

The flight is fully Auto Mode from take off, waypoints, to land.
The pilot does not control the stick until the drone fly fast to right (try to take over using loiter).
What could happen?

Bad aileron stick?