It's likely the pull drift compensation the electric steering is supposed to do. It compensates when there are inconsistencies in the road that would cause the car to drift left or right.
The issue is that it doesn't really work as well as it should...I'd much prefer it just let me handle it myself, but I doubt it's something easy to disable.
I also doubt you'll get it "fixed", as there is likely nothing wrong with it. Maybe Ford will change the programming a bit...until then I don't see any methods of eliminating it.
Hatch Nation #29