Me Dual DC Motor Driver vs ME Orion onboard Motor Drivers

#1

I want to drive 4 identical DC motors using the ME Orion board and the ME Dual DC Motor Driver.
In mBlock i use ‘set Motor … speed …’. This works well with the motors connected to the Dual Motor Driver, but the two motors connected to the Orion board itself stutter.
Can someone explain why this happens? The Orion board is powered by an external 5V power connector.