Mouth Controls seem to have odd rotations when Jaw control is rotated

Head_Top_Mouth_Ctrl and Head_Btm_Mouth_Ctrl seem to slant to the screen right (if looking at it from the front) when I have the Follow Mouth Corners turned on. This looks terribly broken. Surely it should be following both sides and not favouring one over the other? First image is closed pose, and second is the jaw open.