Beside using the ****ing rope, are you using broad heads?
Field point tipped arrows will fly one way, broad head tipped arrows will fly the way they feel like it.
Back to the rope ****er. They really do make the shots...AND shot to shot more accurate.
One thing also, about Barnetts. When you slide the back of the arrow back against the string...make SURE that the moon nock is actually against the string.
The string holder (don't know the real name..!) is larger around it's locating pin than it should be and the back of the arrow will sit up a little off the track on this piece. When sliding the arrow back...it will hit "two" hard spots...the string holder (?)...THEN...the string.
Make sure you push hard, the same way every time.