Electronic system goes off & on while driving, dash components, lights air etc. on 2005 Ford Freestyle

At first I thought the whole car was stalling out and coming back on but actually the gas pedal is still responsive and when this happens the system even gets a little boost of gas and slightly increases speed for a second.
It happened a few times in the fall on hotter days but now that we are over 70 degrees pretty regularly it happens multiple times while driving every day under all conditions (Wet, dry, hot, slow, fast, during acceleration, driving at a steady speed, highway and back roads.) On the way to work it turned off and on 5 times in a row in rapid succession.

Both the dealer and another chain repair shop tested the electrical system. The voltage and battery were "fine." They could not find a problem. The one place drove the car and did not replicate the issue.

I get regular maintenance I am due for my 100,000 mile tune up because I just hit 103,00 this am. I have a new battery and don't want to just start replacing things because no one can figure it out.

Other issues with the car:
Driver seat heater not working
Cooling dash component does not light
Left rear tail light and housing replaced in the last 2 years due to the housing being cracked (water did get into the housinging at that time)

Any help is welcome I do not want to be taken to the cleaners.

Asked by for the 2005 Ford Freestyle