I have to agree that the way James's voice glitches from an E down to a C sounds like an autotune glitch, because of the way the vocal timbre changes so much on its way down (gets a lot lower just as an audio file does when its transposed down).
But I don't care. It bothered me on the first few listens after I heard it, because it was tough to un-hear, but it's such a minute thing that I stopped caring after a while.