What sleepy says is correct, however, I still think it's a nock point issue and/or perhaps brace height. If your brace height is real low, and you have a low nock point, the arrow will hit the shelf before it clears the bow. Of course, the arrow can still hit the shelf with a higher brace if the nock point is too low.
How do you have your nock set now. If you're shooting5/16 diameter arrows, I recommend you start with a nock point 7/16 to 5/8 above square ( and nock under). Go up another 1/16 if you're shooting 11/32 woodies.
Good idea to also use two nock points, one above and one below the arrow, so the arrow doesn't slip down at release.