One thing that I have noticed that card clumping happens more often in the morning when fresh decks are in play rather than in the evening when the cards have run through the shuffler. This is what I have seen happening for about the last 8 years. I have been playing BJ for 20 years and never seen it happen so much. I have counted 300 shoes and about 100 of them I consider to be excessive in clumping. In one shoe I saw 19 face cards in a row and not one ace. Don't know if it means anything but it sure will make you think.