Hi Sean,
Thank you for the additional tests and explanations.
This issue you are experiencing has already been encountered by other users and was reported in this post.
From previous logs investigation, it seems that the issue originates from DJI SDK or drone firmware. However, it is interesting to notice that the issue does not occur on Android.
Would it be possible for you to send the logs of the flight you did having this yaw angle on iOS? For an efficient investigation, it is important to notify the date and the hour of the flight, and the mission name if possible.
Best,