I have a Pixhawk on a large wing so using elevons. I ran Autotune and it seems pretty good but about 25 minutes into an Auto flight I got a bit of oscillation. being elevons it’s more difficult to tell if it’s roll or pitch but it looks like roll to me. Have a look at the video on YouTube https://youtu.be/yKi6KQ3VrBM
PID values after Autotune below too. Some well above recommended max.
2nd issue is after a few minutes into a flight I get the Error Compass Variance warning. The compass is configured OK (external only) and Onboard Mag Calibration completed. See photo below. Any ideas?