I believe you’re right there‘s something going on with the 15s, at least with the Pros. I wouldn’t even know if I weren’t syncing my phone to my Mac, everything functions properly except for that syncing. I have been able to back it up with no issues. Again under Mobile Devices in Library/Logs my phone doesn’t even appear. It appears to sync but nothing that I can tell is offloaded to my Mac. My iPad Pro goes through this process as expected. I even triggered a sysdiagnose on my phone and then did a sync, even that file was not picked up. I could Air Drop it to the Mac, but it wasn’t transferred by a sync.Over the weekend, I even did a full restore using my encrypted backup from Mac. I'm out of ideas so just chalking this up to 17.0.2 with 15 devices. Hopefully will resolve itself when 17.1 public gets released.