Chris- can you explain how canting the bow changes spine? I have never heard that before.
Jayman, perhaps when you cant the bow, the wide shelf somehow contacts the arrow as it passes, throwing it off? You could put some crayon or lipstick on the shelf or arrow and look for evidence that it's hitting. Also, notice your string havd and confirm that you are not twisting the string due to the cant. For me, canting doesn't have a noticeable effect. Does your bow have an elevated rest, or are you shooting off the shelf?