A #Netflix guideline many #subtitlers don't get: "Avoid going back and forth between italicized and non-italicized subtitles when the speaker is on and off screen. If the speaker is on-camera for at least part of the scene, do not italicize. Leave italics for off-screen narrators

The concept of "scene" may a bit blurry in documentaries. One way to distinguish the change of scene may be thinking in terms of a new paragraph in written texts: change of topic/focus.