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Hi, I had an identical problem with my 2007 Expedition. I went through the the usual starter motor, battery ( was recently changed). The last thing I did was to swap over the starter relays. I swapped them with the trailer towing relays( same units). The relays are #57 run/ start relay and #54 starter relay. swapped with relay #55 towing and #56 towing lights battery charge. Since then no issues with the truck. BTW relays are in the box above plastic radiator shroud in front of the motor.
Hope this helps.
This is going to sound weird, but your Truck needs a Reboot, and to clear the KAM(Keep Alive Memory).
Pull the battery cables, turn the lights on. Wait a few minutes. Turn light switch off, and reconnect battery.
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