If the connections between motor and Arduino shield are not really fastened and get loose while the shield and Arduino are powered your electronics can be fried due to the back EMF, caused by the inductance of a motor.
When a powered motor gets unconnected this back EMF can rise to values which destroy the still connected device (shield, Arduino).
So always either use screw terminals to connect a motor or solder it.
Looking at the attached image you have the shield v1 which is meanwhile substituted by v2.
Here is a detailed instruction, how to use v1 shield:
Addit:
pls use code tags </> when posting a code.
Reading the forum rules is also a good idea.