Hello,
I am sure this folllowing issue is due to my own stupidity, however i would like to try to understand what happened so that i (and others) are aware of this.
I just had a very interesting experience operating my ardupilot based copter today after adding the Herelink air unit to the payload.
I am using the Herelink for video, RFD900 for telemetry and ELRS 2.4GHz for manual control. Knowing that two of the systems run on 2.4Ghz (Herleink & ELRS) i knew that i was risking interference but i thought that my RFD900x link would work as a backup and that i could at least change flight modes and initiate an automatic landing in worst case.
However… Shortly after takeoff and climbing 20 metres the interference started. It started controlling the copter, demanding random pitch, roll and altitude changes. I quickly took my GCS and commanded BRAKE mode to lock the copter in its position, disregarding the erratic control inputs it was recieving. This worked… for a few seconds… The interference was also switching randomly on my FLIGHTMODE channel. Unfortunatly the flightmodes i had set-up were Alt-hold, Stabilized and Loiter - a very bumpy ride.
Luckily i managed by chance to land the copter and disarm with no damage. It was a miracle.
I think i was expecting a more robust protocol on the ELRS system that would not accept the interference as actual control inputs. I now plan to use the herelink for video and telemetry and the RFD900x for control, ensuring the two links are working seperately on 900MHz and 2.4GHz.
If anyone has any input to how this sort of interference can be avoided, let me know 
Won’t try that again