Below are the content issues:
1) Natural Disasters Course puts many of their content headers into its own unit, which doesn't render well in the mobile app (since they are shown on multiple pages)
2) In 'Greatest Unsolved Mysteries of the Universe', in 'Any questions?' after intro, there's a calculator icon in the bottom right. Clicking it opens a field for entering calculations. Pressing 'i' overlays what looks like some help text that isn't fully visible.