Lately I've been experiencing random issues swiping from article to article within my collections. It simply just wont do it. If I pinch out or goto the browse page and back into the article, it will resume swipe capabilities. This happens at random and in varying collections. I have rebooted my device and re-downloaded the preview app a few times since this has been going on with out change.
As a side note:
It gets weirder; there was two occasions yesterday when I was trying to swipe up or down through my article pages and the app would swipe to the left or right depending on if I was swiping up/down.
I'm having some similar problems on when viewing articles only on my phone. If I accidentally start to swipe to the left or right (but not enough to go to another article) it will no longer swipe up and down until I complete the swipe to the next article (left or right).
I'm running iOS 9 on an iPhone 6.