I think you are right about the hazard lights.
This morning I went to do the test again, and the light did not turn on!
However, I drove around the park and afterwards, the truck failed the test light check again, and again the same circuit.
I could try to replace the whole harness, but if I can find the exact problem, the repair would be a lot cheaper.
Also, as far as I can tell, there is more than one harness involved in the circuit; in the engine bay and under the dash, so that could be hit or miss.
I am looking for information on how to use the test light or a multimeter or even just common sense, so that I can find the problem (short) wires and replace them.
The Bronco Graveyard has an aftermarket headlight harness for sale, and they are relatively cheap, so I could try my luck at fixing the problem by replacing mine.
However, I do not know exactly where the wires short and it could be on a different harness.
I am going to check the fuses under the dash again with the door closed, maybe I can narrow it down.