Okay. If you have a tool that will monitor your sensors in the PCM then we need to start looking at what the PCM is seeing. I suspect you have a sensor issue that you have not replaced yet or wiring to one of them.
If you look at the wiring diagram I attached, this is from Ford and it states on it that the overdrive light will flash if a sensor/actuator or circuit has failed.
I highlighted the sensors that you need to look at and write down what they are reading when the engine is hot. Then monitor your speed sensors that I mentioned above while driving and see if they match the speed you are driving. You may need someone else to drive for you for this part so you can monitor them and write them down or video them while you are driving.
If nothing stands out, send me the results and we can go through them together.
Based on everything you have done, I suspect you have a wiring issue with one of these sensors, so the PCM is not getting a good signal and disengages overdrive. Using the scan tool is easier then checking each of these wires for short to power/ground and checking resistance.
Image (Click to make bigger)
Tuesday, May 4th, 2021 AT 10:07 AM