Interactive elements in book chapters should only be enabled for the current chapter. For example, opening a book with videos or audios with autoplay enabled should only play for the current chapter. When changing chapters, the video playback should resume the status they had before (paused or playing). Iframes should be disabled entirely (removed from the screen), because it's difficult to control what they have inside. But they should reappear once a chapter is opened. Exact testing instructions: Open a book including iframes and autoplayable elements in different chapters. Change chapter, and check that the elements in the previous chapter are paused. Manually pause an element, go back to the previous chapter and the elements should resume playing. Go back to the previous chapter; the element that was paused manually should not resume playback. During these interactions, iframes should be removed and added again every time the chapter is deactivated / activated.