dougp:
Per the photo it doesn't look like the ground side of the resistor is connected to ground, maybe I'm not seeing well. Should you not also have a resistor to ground for channel B? What happens if you swap the blu/orn wires on the Arduino header?
Added to resistor to pin B as well, no change. Swaped the wires in the arduino PINs A and B, no change there either.