Interference? Channels not all working

Hello, I have an issue with my drone and no idea where it comes from?
I have a PX4 (with orange cube) in my drone, an Here+ as the controller and a Raspberry 3B+ connected on the serial2 of the PX4. The RPi listen the mavlink RC_CHANNELS messages sended by the PX4.
On the Here+ I setup a button for the channel 11 on momentary press and so the RPi listen and do something if the value of the channel 11 is higher than 1200 (arbitrary chosen).

Everything works, I also made some flight and it works without any problems. But yesterday I made a longer range flight and it stopped working (the RPi never received a value higher than 1200 on the channel 11 when the button was pressed).
I have several hypothesis. Maybe the signal is just never received (but since the stick was still responding it would mean that there is in fact one signal for the channel 1-4 and one signal for the rest)
Or maybe the signal was lower than 1200 maybe due to distance but since it is in µs is no very probable.
Maybe interference?

So I don’t know if you can help me? Or if one of these hypothesis is possible, or if I should do that in another way


Your log file is the place to start.
Post a log file from the flight controller and interested people will comment.
Not much we can say from your description.