How can Bank B stop payment on the official check that was purchased with fraudulent wire fund?
You can't. The Uniform Commercial Code will place liability on your bank for returning its own cashier's check as a stop payment. The legitimate party that gives value for the bad guys negotiating the cashier's check cannot be on the short end of this stick. This is between Bank A and it's customer as to who bears the loss. You do not have a dog in this fight and I don't advice sticking my hand in between the two and risk getting bit, yourself.
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