The Orientation setting in the editor for Android phones does not respect the user's settings. Despite "Auto-rotate" being turned off, the orientation of the UE4 app will change if it is set to do so.
This may be expected behavior but it does not seem like good UX to me.
This occurred in 4.20
There's no existing public thread on this issue, so head over toAnswerHub just mention UE-70556 in the post.