The X motor is a Stepper Motor: Bipolar, 200 Steps/Rev, 28×32mm, 3.8V, 0.67 A/Phasehttp://www.pololu.com/catalog/product/1205
The Y motor is a 57byg stepper motor:http://www.act-motor.com/en/product/20130617/66.html
I verified that the power select switch is on 5V.
I tried reversing the 2A and 2B on each channel. I get the same buzz but not as strong. I can hear the program cycle through the 3 settings step modes with different pitched buzzes .
I added a picture of the wiring, minus the extensions. I have tested them with the meter and with the other motors.