Problems with left arm

[pearlslugs]

I retargeted to a new mesh I made, I used Autorig Pro so I dont think its a weight problem, none of the ik or twist bones have weighted vertices, but the left arm is always moving out of what ever layer blend its supposed to be a part of.

For instance, lets say I'm using the two handed rifle layer blend, my characters left arm will move to the standard position and back to the rifle position. Any tips?