Engine shut down

I answered this question yesterday. I'm suspicious that the torque converter clutch (TCC) is coming on in reverse, especially suspicious if it only does it only when warmed up. I think you should take it back to the people who rebuilt or installed your transmission and torque converter. If you don't wnat to or can't, find a Ford specialist or transmission shop you like and get it diagnosed. If you want to find a specialist, here's a directory link for you: https://repairpal.com/ford-repair-in-san-antonio-texas