I have a few bugs to report, and this appears to be the closest thing to where I would do that.
First, the "skip to next" button, iOS 9.2, iPhone 6 plus. Crashes every time.
Second, if I download a lesson, and listen to it streamed, it doesn't put the media player controls on both pages, even though they're the same page, same lesson.
I'm going to guess it's a navigation controller that pushes a the same VC either way, so whoever coded your model missed something.
I believe the "skip to next" crash happens also on the lock screen, as it just stopped when I hit the "next" button. I know you guys just hired an iOS programmer last year, so tell him/her to get these things going. I make too much here to justify coding in Japan, but if I can make my own app and get it going, then the revenue won't be an issue and I can go fix those bugs, hehe.
Let me know if there's a better platform for bug-reporting, or if you don't have an iOS programmer and want these fixed. If they used HTML5 or Xamarin, well... the app responds too well to be HTML, uncertain about the other one, just C# though.
(I did weatherCaster's UI and SmartGlass UI, familiar with iPhone quite)