Props to app.net@clarkgoble for clueing me into this bug. I’d been seeing iTunes/iPhone sync hangs with my device, but when I returned iTunes seemed to have completed. I forgot, probably because I’m tired of tracking Apple’s issues , that iTunes “swallows” fatal errors during device synchronization. In retrospect it wasn’t completing sync.
The clue that I had a real problem was that I couldn’t get new Audiobooks, which must be transferred by old-time iTunes sync because they’re stuck in the 00s, to show up on my iPhone. Clark’s app.net note gave me the idea to turn off photo sync. With photo sync disabled iTunes put the Audiobooks on properly.
There are two Apple issues here. One is an iTunes/iOS bug with Aperture (and probably iPhoto), the other is that iTunes hides serious failures from its users. There’s not much hope for either bug. Aperture/iPhoto have been abandoned (as best I can tell nobody uses Photos.app) and the iTunes error-handling problem is quite old.
I’m going to also disable my Aperture screen saver module to further isolate Aperture for OS problems. Now that I have a workaround for Apple’s ancient network share photo slideshow bug I’ll just export our slideshow images to a thumb drive hanging off our Time Capsule.
 Apple’s software engineering issues are impressive. At this point Tim Cook has full responsibility — failure of a major organizational function is always the CEO’s responsibility.