Good News and Bad News...
Good news is you probably don't need a new lock cause it an easy fix... but the bad news is, it is a bitch to take the whole thing apart.
I had the SAME exact problem on the SAME exact door, only on my zx5. You need to get the actual electronic mechanism out, in your hand, away from the door. Take that apart till you see the wheel in there and the motor, and make sure it moves freely. I did this, and what seemed to happen is that the gears jumped a step.. and they need to be put back literally. I fixed it, and it works now.. FORD wanted to charge me 50$ to check it out, and probably would of charged me over $100 to get a new lock..
It took me an hour to fix it with the help of my roomie.