At Trick 10, East manages to lead the only wrong card, the ♥6 from under the ♥A.
Down 1 instead of Down 2.
The East GIB has an exact count on the hand, having seen West show out of spades and South show out of Diamonds.
I think the problem here may be an unnecessary reliance on the opponent's bidding.
South's 4♠ bid allegedly has 11- HCP, so the one heart he has "can't" be the ♥Q by that logic.
However, there is only one non-trump left to take, so there is no advantage in trying to let West win it. So, take the Ace!!!