Strange Yaw Perturbations in Auto Mode


I’ve encountered some odd yaw behaviour with a Y6A in auto mode (although I have come across it myself once or twice in stab). For reference, the aircraft is around 1kg, with 2206 motors and 6" props. Autotuned a while ago, and pitch, roll and excess power are amazing to fly.

In a lot of auto waypoint flights, the aircraft will at some point have a large, sudden yaw perturbation, sometimes up to 90 degrees or so - sometimes it can catch it and return to the waypoint, others I switch to loiter to stop it deviating too far.

I’ve had a dig through some flight logs, but couldn’t find anything overly out of the ordinary. - I’ve attached one such log here. One of the yaw movements is very visible starting at approx. 6m and 8s. A spike is visible in ATT.Yaw, but interestingly to me ATT.DesYaw also spikes - just not to the same magnitude.

I’m planning on heading out to attempt some additional PID tuning of the yaw axis - as it’s a bit lethargic anyway. Is that likely to be the cause here too, or are there some other gremlins in there I’ve not seen?