I have been using the v2 Motorshield for various projects without any issues until now.
When I power the Motorshield (using 12 V), the "Power" LED blinks on and off (white light) very quickly. This is the LED that usually is green when the Motorshield is getting power. I have not been able to find any answers in other threads, so I am trying here.
I have the Motorshield on the Arduino Uno, using a 12 V power supply connected to the power/ground rails on a breadboard, and wires from the breadboard to the blue wire blocks on the Motorshield to power the shield/Arduino. I have a 12 V DC motor plugged into the M1 motor port, and a few digital and analog I/O pins being used as well.