Short circuited some pins on a stepstick, now Sanguinololu is broken (i think)

While settting the correct Vref for the driver current on my "Ice Blue Stepsticks" I accidentally short circuited two pins on the Stepstick:

• the GND pin on Y-axis stepper
• the VMOT pin on the Z axis stepper

(check screenshot & [www.think3dprint3d.com])

Now the Y-motor is shaking and ratteling and makes a lot of noise (no more fluent movement like before).

I tried to determine the cause by doing these steps:

• Y-motor on Y-stepstick = NOK (shaking & noise)
• Y-motor on X-stepstick = OK, y-motor runs smooth, makes me think the stepstick or the motor is broken
• then exchanged the X and Y stepsticks = Y stepstick driver is in X position on sanguinololu now
• Y-motor on X-stepstick = OK, y-motor runs smooth, makes me think there is no problem with the stepstick but the motor is fried
• Y-motor on Y-stepstick = NOK (shaking and noise), proves to me that motors & stepsticks are FINE!?
• X-motor on X-stepstick = OK
• X-motor on Y-stepstick = NOK

So this pinpoints that the problem are not the stepper motors NOR the stepper drivers?
Can I then conclude that my Sanguinololu 1.3a is fried somewhere? Can I test this in any way?

I can still connect to pronterface and send all commands and the printer reacts. Only for the Y-axis the motor starts ratteling (on all kinds of Vref voltages)

Shall I buy a new Sanguinololu or does anyone know where to find the bug here?

Ice Blue Stepsticks: [www.think3dprint3d.com]

Thanks in advance for your time and expertise!
--Kenny