I've always had tons of bugs trying to play audiobooks on iOS (iPhone 6, iPhone 5, and older iPod Touches). But 9.3 (including 9.3.1) is ridiculously bad on my iPhone 6. I get crashes, especially if I try to use the skip ahead/back buttons more than a couple times. Constantly loses my place. Fails to start playing sometimes, or requires 6-10 play button presses to start. Sometimes starts playing from two different points in the book at the same time. Books are almost all from Audible.
I'm baffled how Apple can't get this right after so many years.