Still struggling with this. But here's the latest. First, I don't seem to have a Reset Sync History option. And I don't think I'm actually signed into the iTunes store on the iPhone. Unless I'm missing it - the phone is new and I haven't used it for any purchases since.
Here' s something new tho - I tried simply unsyncing so I could resync in small increments and watch. It's always been set to sync only checked playlists so I unchecked them all. In a few cases, it made new playlists that were checked, i.e. next to a playlist called "Lisa's Favorites" that I'd unchecked there was now a checked playlist called "Lisa's Favorites 1". These dupe playlists have occasionally happened in the past and I just delete them but it did this with maybe 5 of the 20 playlists I unchecked. So I deleted all the dupes and literally unchecked the entire Sync Music option and applied it. The music is still there (though with no playlists anymore) on the phone ...BUT the albums are fine - no dupes. Another thing that might be helpful info for diagnosing is that, within the albums that were full of dupes, there would be some songs that were not duped. Made no sense as the albums were all acquired in the same way. But it looks like the ones that only had one copy are all tunes that weren't in any playlist of faves. Wondering if this might be a leftover from an earlier device where had to babysit the syncing so as to not fill it up and these non-favorites weren't duplicated somewhere that the ones I'd starred and put into playlists that I synced are duplicated...?
One more thing (sorry this is so long) - I'd been having trouble with the artwork not syncing right before I noticed the dupes. That now also seems to be almost all correct in the music that's still on the phone.