Varun Aaron had a good explanation, he was saying hand made balls ought to have a bad batch. The problem here is the Quality check, a bad batch may be produced but how did that miss the quality check?
Also Dukes is used by WI as well and was recently used in the test series, don't know how frequently was the ball changed there.
Dukes can be banned, but the only options remaining are SG and Kookaburra, Kookaburra is of no use in English conditions, only if SG starts exports it would be good option.