My son has a Stick and it shoots just fine for both of us. As Arwin said, you need to have your hand about level with the shelf, which is what I like on any bow by the way. Also cant your bow. Shooting a Stick held vertically is an exercise in futility.
Another thing to consider is if your arrows are spined correctly for your bow. The Stick is NOT cut to center, so correct spine is critical. If it is too stiff, your shaft is hitting the riser instead of bending around it, which would make it feel as if it is falling off at the last second. If the arrows are just a little bit too stiff, they will usually hit the riser with the nock end and kick right (right handed shooter). If they are a lot too stiff, they just won't bend around the riser and will head left due to contact along most of the shaft. To avoid cutting your fletching, try shooting cock feather in.
As you can see, there are several possible causes. As Pygmy pointed out though, the bow isn't usually one of them.