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. Onboard video footage here
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?