Make double sure you're not torquing the string, especially if your letoff is more than 65%. First time I looked in a mirror with a fingers draw on an 80% letoff bow, I about had a cow! I was having trouble getting a good tune and my accuracy wasn't what I expected, so I checked my form by drawing in front of the mirror.

Lo and behold! There was an 'S' curve twisted into the string, because my bow was straight up and down but my wrist was turned out about a 30 degree angle at the bottom. Rather than the string tracking straight from the top cam, through my fingers to the bottom cam, the top half of the string was a good inch offset from the bottom half.

You gotta make sure your string hand wrist is aligned with the string so you won't get that twist.

Don't know if that's your problem, but it's definitely something you must check. [&:]