[Powerhouse]

I changed the Artwork on one song, and it changed the Artwork for every song on the Album (great).

I really have not been able to repeat that myself, or even image how it could happen. Are you are that you didn't change album art instead, that would effect every song. Otherwise can you repeat it? 

Album art is indeed what was changed, but remember, the dialog called this "Thumbnail". It would actually have been better if the dialog called it "Album Art".

So to be clear, I selected a song, and changed the "Thumbnail" (Album Art), to the Artist Thumbnail (Poster), and this changed the Artwork for every song under that Album to the Artist Thumbnail (Poster). When I went to change it back to the correct "Thumbnail" (Album Art), it only changed it for an individual song, not all the songs in the Album folder (as the first change did).