Machida says he rewatched the fight multiple times in order to ascertain exactly where he lost his composure. He thinks he was hit in the neck with an illegal elbow. Looks like he hit him just above the ear (which is legal), IMHO.
That looks pretty darn clear. He got hit on the side of the head. The way his head was tucked and his shoulder was up there is no way he could have been hit below the ear on the neck.
IIRC that was the shot that put him on rubber legs, right at the end of the round. His corner could've stopped the fight between the first and second. I haven't seen an angle that makes it look like he gets hit on the neck or back of the head. Then again he was the one who took the shot... In any case I think this is unbecoming of Machida. He's usually above this kind of excuse making. Maybe he's finding it difficult to transition from a contender to a gatekeeper?