We've reproduced this in several books on iOS.

Steps:
1. Download a book
2. Tap play
3. Pause after a few seconds
4. Return to Detail page (don't close app)
5. Tap Listen (or read).
6. Pause will show correct timecode
7. Tap Play

Either audio does not start playing, or other times play will jump back to 0:00 in the track but still won't start audio.

Usually closing and returning to the book again, using TOC, or closing app after pause does allow normal pause/play interaction. So this bug might only show up when starting play/pause while remaining in the player/detail-view modes. We'll have to test more to see if this holds true in all cases.