Quadcopter gives Radio Failsafe and climbs to 15 meters immidiately after arming

I was having the second flight after the first succesful flight attempt with my 3 kg quadcopter. It has a Pixhawk Cube Orange+ and the latest ArduCopter firmware. It is powered by 4 SunnySky X2814 motors with 1155 carbonfiber props. I am using the FlySky ia6b received and the FlySky i6x transmitter.

I have armed the motors on stabilise mode and asked my ground station operator if there was anything wrong going on on the mission planner before taking off. She responded with that there was a error message about the radio, then the quadcopter flew up to 15 meters. I hadn’t touched the sticks of the transmitter after arming the motors. It stayed there for about 10 seconds and then made a free fall from the sky, completely stopping the motors. Those 10 seconds were also not stable, it was shaking back and forth. Transmitter battery voltage was 4.9 volts. I later realised this might have caused the problem but could not understand why it went up after losing the radio connection. The failsafe setting was “off” for all channels on the radio transmitter and I had not set any radio failsafe on the Mission Planner.

I have added the .bin file of the flight.
2023-04-17 15-43-39.bin (616 KB)

It shows a 1000 to 2000 signal change after the arming. It shows several radio failsafe messages and a motor emergency stop that I did not initiate. (Motor Emergency Stop was on channel 6 but i have not touched it during the flight.) Do you think a jammer might have caused it? I had heard that there were some special security zone 500 meters east of were we fly but nothing like that (nothing regarding the radio connection) ever happened before during our more than 30 flights with different drones in the past 2 years.
I can not understand what happened to cause that kind of behavior. I appreciate and thank for the any and all help you will give.

After arming you had a Radio Failsafe triggering RTL. It then climbed to RTL_ALT where it looks like panic set in (Loiter, RTL, AltHold Stabilize). Finally it was in Stabilize and you dropped the throttle entering the ever famous Rapid Return to Earth Mode.

There were multiple radio failsafe events triggering again RTL until you changed modes manually.

It looks like you have done no tuning other than the Initial Setup Parameters.

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Oh, I see… Thanks a lot. Can the ardupilot initiate the RTL mode while on the ground and armed? Just asking of curiosity and fear of something like that happening again.