The automix queue feature seems to not add songs that are added through search and find. The songs that are added by swiping through the list works fine, but when a song is added by searching and tapping, the song does not appear. Once I have gotten the search-added songs to appear (not knowing how I did so!) only to find that it had been added multiple times (because I went back and tapped it many times thinking it was just being slow and not adding to the queue.
If any clarification is needed, please let me know.