I have the same problem. it sucks! ! or 2 cards flip off the deck ALL the time.
I emailed TG Murphy himself about this problem and this was his response to me, hopefully it can help you out. Im still working on it....
" Hey Pete,
Having helped many people with this let me take an educated guess as to your problem area.
Often, the problem is in the release of the packet or deck.
The release must be clean, smooth and sharp. Do not throw or toss the deck.
In other words, do not have the finger(s) slowly release the packet or deck.
If you are using a two or three finger release try using only one.
Eventually, most beginners end up using only two or one finger release anyway.
Also, I do not recommend a new or slick deck for beginners as this only magnifies some of the beginner’s problems.
Instead, try using a worn or used deck that does not have any bent cards and it may be helpful to have the deck slightly concaved.
Make sure the deck is cohesive and together when it is squared.
Try doing the Deck Flip with the entire deck first before attempting any of the other variations which require a slightly different feel to it.
When personally teaching the Deck Flip to others, I have discovered that it only takes several minutes to master it. So let me add that if you are still having difficulties either send a video to this message board of your Deck Flip for further specific suggestions. But first, try this, place the deck into the card case and try the Deck Flip again. By using the card case, I think you might resolve your own dilemma.
Finally, the flipping or rotating of the deck is very important, but, when starting out so is the left hand once the deck is in midair to correct any problem with the flip. What I mean by this is by moving the left hand downward while the deck is in the air will allow the deck more time to flip or by moving the left hand upward will allow the deck not to over rotate because the flip was too fast. Likewise, just like catching a ball that was tossed in the air, the left hand may have to move to the right or left in the beginning to catch the flipping deck. But, once the flip is mastered, then, the left hand rarely needs to make these adjustments.
I hope you get my Deck Flip down pat as I am writing another book that has many new sleights and flourishes using the Deck Flip as a prerequisite.
Good luck!
Imagicatively yours,
T. G. Murphy"
Hope that helps!
p:m