USB connection lost with XDC2230

we have strange issue. We have a differential drive setup with two independent DC motors. we are getting a connection lost message only when both motors are spinning in counter clock wise. we couldn't observe the same behavior when motor is spinning in opposite direction (clockwise and counter clockwise) and also when both the motors are running in clockwise. Please let use know if need any further info.

Also does the length of the USB cable have any effect on the connection?