I was having this same problem with my newest bow and found two things that seemed to cause it.

When I first got the bow, it was set up and ready to shoot so I didn' t worry about tuning it right off. I just shot it as is it was to get a feel for the bow. Every third or fourth shot, I would get a slap on the wrist. Once I put a new rest on the bow and tuned it properly, the wrist slap was greatly reduced, but would still happen. It wasn' t hitting me as hard or as frequently, but it was still there. I found it to be my stance as C903 described. If my feet are positioned so that the target is directly to my left and my feet are almost in line with the target, I get wrist slap. If I position my feet so that they are about 40 to 45 degrees to the target, I get a perfect release and much better accuracy.

The best way I can describe this is that your bow hand, your release hand and your left shoulder (right handed shooter) should form a triangle when the bow is at full draw. The better you can repeat this triangle, the more accurate you will be. If your feet are lined up with the target, your left shoulder lines up much closer to the line between your bow and release hand, which closes the triangle and brings the string much closer to your arm. Thus you get the wrist slap.

If you line your feet up so that they are at a greater angle to the target, you open the triangle up so that your left shoulder is farther from the line between your bow and release hand and the string is farther away from your arm upon release.

Once I figured this out, the wrist slap was eliminated and my accuracy improved greatly.

The draw length mentioned above will also cause the same thing. If your draw is too long, you will be forced to turn your body more to reach full draw, which will bring your left shoulder much closer to the line between bow and release hand and the triangle will be much more closed. If you can' t draw and anchor comfortably with your feet at a good angle to the target, your draw is too long and should be shortened.

Good luck getting it sorted out. Hope this helps.