Listening to Ray's raw vocal track, I noticed he was nailing notes spot on, and missing some completely. When I reached the end of the first chorus, I distinctly heard Autotune mis-tracking. When I looked at the tracking in Autotune (graphical mode) I could see instances where the vocal notes were jumping to notes that were not in the scale. It then occurred to me that the track was processed in Auto mode, chromatic.
The problem with this is the following: If by chance you are slightly flat or sharp, Autotune will correct the note to the closest note in the allowable range. If you're set to Chromatic, it's very possible for F# to come out as F natural. This usually only happens during faster note passages because the singer is moving past the notes much faster. Take a listen to the last line in the first chorus, "well I never want to lose those funny things..." (This is at about 0:50 seconds into the song) Ray is a better singer than what you hear on the passage. It's just that Auto tune took him way off the mark.
Not that I'd ever recommend using Auto mode in Autotune, however if you did, it's much better to set the key of the song - in this case G major. If you have a case of the singer singing some blues rifs, then you can add the notes required. The best way to do tuning is to only fix the notes that need it. Oh, and use Graphical mode!