Dagu 4 motor control cuts 2 motors off at 120 speed?

I hope this is the correct area, I am trying to isolate a hiccup I think may be related to the dagu 4 motor controller card (red). 

I am using it on the Rover 5, 4 motor version. Channel 1 and 2 are the right and left front motors, channels 3 and 4 are the rear right and left motors (Channel 1+3 = Right front/rear).  The motor power supply is direct from a 7.2 NiMh Batt. The motor Logic is from a 5v regulated supply from the Mega2560. 

The problem I am trying to isolate is when the code switches the motors to reverse.  My rear 2 motors stop running if the speed is set to 120. 

I rewrote the code to experiment with this annomily, only.  The rear two motors will not come on with the speed setting of up to 127, but as soon as I hit 128, they start turning (just (+1) above the halfway mark to the max speed of 255)

The only thing I can think of, When I decided to use this board with this platform, I had to reverse the wiring on the rear motors in order to get all 4 to go in the same direction.(required for this motor controller or else would require connecting both left motors/right motors to only 1 channel for each side)  So would my front 2 motors, cut out if the forward speed is set below 128? I haven't tested that yet....(the coils on the motor leads have anything to do with it? that is the only wiring difference I can see between the front and rear)

I can't find anything on the motor control or the rover about this... can someone point me toward more info?  Do I have something set wrong?  Here is the code I used to test the minute settings... I don't see anything wrong with it.  

Thank you all!

Ed

 

//Front Motors setup. Original 2 motors.

#define MOTOR_RF 4 //motor Right Front pin4 (right front pwm/speed signal)

#define DIRECTION_RF 5 //motor Right Front direction pin5 (right front forward/rev)

#define MOTOR_LF 6 //motor Left Front pin6 (left front pwm/speed signal)

#define DIRECTION_LF 7 //motor Left Front direction pin7 (left front forward/rev)

//rear motor setup ** make sure 4 motor control pins are reversed!

#define MOTOR_RR 14 //motor Right Rear pin14 (right rear pwm/speed signal)

#define DIRECTION_RR 15 //motor Right Rear direction pin15 (right rear forward/rev)

#define MOTOR_LR 16 //motor Left Rear pin16 (left rear pwm/speed signal)

#define DIRECTION_LR 17 //motor Left Rear direction pin17 (left rear forward/rev)

 void setup()

 {

  pinMode (MOTOR_RF, OUTPUT); //Front right

  pinMode (DIRECTION_RF, OUTPUT); //Front right

  pinMode (MOTOR_LF, OUTPUT); //Front left

  pinMode (DIRECTION_LF, OUTPUT); //Front left

  pinMode (MOTOR_RR, OUTPUT); //rear right

  pinMode (DIRECTION_RR, OUTPUT); //rear right

  pinMode (MOTOR_LR, OUTPUT); //rear left

  pinMode (DIRECTION_LR, OUTPUT); //rear left

 }

  void loop(){

      analogWrite (MOTOR_RF, 128);  analogWrite (MOTOR_RR, 128);//speed Motor Right(front/rear)

      analogWrite (MOTOR_LF, 128);  analogWrite (MOTOR_LR, 128);//speed Motor Left(front/rear) 

      digitalWrite (DIRECTION_RF,0); digitalWrite (DIRECTION_RR, 0);//direction reverse for Motor Right Front

      digitalWrite (DIRECTION_LF,0); digitalWrite (DIRECTION_LR, 0);//direction reverse for Motor Left Front

}