That hinge ground wire failed on all my wagons.

On the wagons that I did not replace the harness, I added a new ground wire. First, I completely removed the old ground (to get the space inside the hinge).

Then I added a new ground wire from a convenient screw inside the tailgate to a convenient spot under the headliner. For that, I found a spot in a strut, drilled a small hole (NOT through the roof!!), sanded away the paint, and attached the wire with a small nut 'n bolt.

For wire, I used instrument test lead wire. That wire (a) is highly, highly stranded so will not break even after a zillion flexes, and (b) has rubber insulation, which stays flexible in the cold.

--
Don Foster (near Cape Cod, MA)