I had a Droidworx ADX4 Coax Octo which during a 8 min flight it would just yaw suddenly, and I would have to give full opposite rudder to stop the yaw.
I ended up getting a standard Droidworx octo frame and migrating the parts across.
And guess what, in 7 mins, it yawed suddenly twice. One straight after a descent from 30m to 5 m, and a second time it turned 90 degrees left whilst at the hover at 1m.
As part of the migration I wrapped the power wires with RF insulation mesh.
I've checked the logs and compared that with the onboard video. The magnet and inclination values were pretty constant, and so were the motor current draws.
I see on that the compass value changes from pretty much north to west, which is consistent with the video showing the aircraft yaw from pointing north to pointing west.
One thing that did puzzle me was the "R/C stick" values in the logs showed Y=-27 and some other minus values as it was turning left. I'm not sure whether this negative Y value is a result of me pushing right rudder to stop the yaw, or weather it's a fault RX causing this.
I have removed the GPS and navi board and put the nav and gps board from my CX4. Will test fly again tomorrow.