Ford Focus 2010 Problems

Without being able to assess the action of the system it's hard to comment, other than perhaps it is doing what it's designed to do. If you're concerned about it, take it back to you dealer and have them assess it.
 

Your dealer appears to have been helpful in trying to address your concerns, so I would stick with him at this time. But I would request that he asks a Ford representative to drive the car with you to see first hand what your concerns are, and than they could explain to you why they believe it is a characteristic of the car, if that's what it is. If that doesn't bring a resolution to your issues then you really have no alternative but to seek a resolution in the court.

We haven't had any other reports of this happening on the Focus, and from your reports it seems it only happens on the one stretch of road. Go back to your dealer, who seemed to think it was a problem, and if he still agrees that it is an issue ask him to arrange for a Ford representative to assess the vehicle on the strip of road where you experience the problem.

Persist with your complaint for a little while, at least, but be warned that you're unlikely to succeed. Use a different service station is the best way to go.

It's impossible to say what's wrong with the car without running a diagnostic check on it, so get it to a dealer to have that done. I doubt that it would cost you anything as the car is still under warranty.

Without driving the car it’s impossible to comment on whether it is slipping or not, for that I would suggest you take your car to an auto trans specialist and have them drive it. In the meantime drive the loan car and do your own evaluation. Your experience is another example of why it’s important to have an extended test drive before you buy.

It could be interference from other sources, such as phone towers, but normally you would find that it happens at the same place every time, and when it does you should be able to see a phone tower or something like that nearby. If it happens randomly I would look for some other cause. The immobilizer is a good place to start, it’s possible that it’s not communicating with the car’s computer, but it’s a very difficult problem for a dealer to diagnose when the problem can’t be replicated. Perhaps also consult a locksmith.