Smoking Servo

New to the forum and robotics I've searched but not found something to my specific issue.

I've Just received a brand new Developer Kit - one of my continuous rotation servos attached to d1 on a EZ-b v4 continuously rotated then started smoking and went red hot. At the time I was just setting up, so I had one HD servo plugged into D0 but nothing else was running and my laptop was booting up at the time so the EZ-b wasn't connected wifi.

All the other servos seem to work fine I'm using the 7.4v, 1300 mah lipo. is this a faulty servo or have I missed something?

Many thanks

Chris