Problem with Ardumoto Shield

I’m trying to drive a couple of dc motors with an Ardumoto shield connected to a Redboard. The A side works fine (forward - backward) but the B side will only spin the motor in one direction. When the B side is activated, forward or backward, both the blue and yellow LEDs light up. Suggestions?

The blue/yellow LEDs indicate polarity and if those are changing, the shield is reversing direction. You might double check your motor, it might only work in one direction.