I understand. Trust me, it's a bit confusing for me right now also.
Yes, the FiiO was giving me problems early on with WiFi syncs, but at some point it was working well. When the current issue started, it was with the Samsung not being able to sync either wifi or wired. Then the FiiO started showing the same non-sync issues as the Samsung.
Over the past half hour while the FiiO syncs with errors on wifi, it completed a wired sync perfectly.
And the Samsung won't sync wifi or wired. Nothing in either error log.
You may be on to something about permissions on the FiiO. In the wifi sync settings I have the removable card selected and under it shows 'grant access.' I tap it and I'm taken to the root of the card and I tap select. Yet when I go back to settings, 'grant access' still show. On the Samsung, when I first inserted the card and granted access, the option to 'grant access' no longer appears. So I assume access has been granted to the Samsung, but is not staying persistent on the FiiO. Is access only required for the wifi sync? Because the wired sync now works. Checking WiFi Sync in the FiiO's Settings > Apps, shows that it has permission to modify, delete, and read the contents of the SD card, along with full network access.
I understand that you can't put more time into this, and I accept that. At this point I'd really like to get the Samsung back to where it is able to sync. My preference is wifi, but I'd be happy to have it do a wired sync.
So as always, I thank you for your time, and leave it in your hands if you want to take a shot at getting the Samsung going again. And I'll promise not to mention the FiiO again.