Do you think you could dig up the ford documentation detailing the visits and work done?Not sure how but I had a similar issue with my lariat. Might just have a sticky spot in it. They did The same to me, reflash and was good for 700 miles, reflash and then returned after another 1000 miles. Finally changed out the valve body and it did not return. Not sure of the why though sorry.
It is truly the most infuriating thing... Makes me wish I had never bought the truck. Ford is of absolutely no help in diagnosing it because "there are no codes thrown."
DM me if you don't mind.