Since I made a good number of changes to my tracks, I decided to wipe my 512gb card clean and do a wired sync.
According to the sync window, at file 766 of 28,189 the sync halted with this notation in the status bar of MB:
In case the image is difficult to read, "Synchronization has temporarily stalled for 2-5 minutes while the device processes current file operations. For the next sync, moving the Playlists folder to Music\Playlist in the setting tab will help."
I've always had the Playlists folder off the root of the card. Same as I have always had the Music folder at the root of the card.
This message implies I should change it to Music\Playlists. Does this really make a difference?
Meanwhile the sync has not restarted after 15 minutes.