I have an EPUB for iPhone that includes a slideshow and a pop-up video. Works fine in EPUB interactive preview, and fine on my Mac laptop when I publish it. When I move it to the iPhone, though, there's a strange oblong shape right in the center. I published it to the web and the shape is there as well. https://indd.adobe.com/view/23e9a0e9-195c-45de-89d9-37f0368eacdf . Anyone have any idea where it's coming from?