At 31 years, if the original hinges, you'll probably want to replace them.

The hinge pin pulls through the front and rear hinge plates. The liftgate sags causing the bottom edge to contact the sill at the bottom.

You can see the 240 lift gate hinge sag at the hinge. With liftgate closed, view edge on from the side. As the hinge plate material wears around the hinge pin, the rear hinge plate (secured to the liftgate) bottom edge will appear lower than the front hinge plate.

The rear hinge sags to the point of the bottom edge about making contact with the roof.

The wires are pulled and eventually break. Through the ground wire appears to fatigue and fail long before that.

The second set of liftgate hinges on the 1990 li'l red 245 1990 wagon (M47 II) were nearly like new when I pulled them in 2006 from a Portland, OR area junkyard. Yet the ground wires in each had broken. I did not replace them.

All electrically works well with that liftgate. I replaced both hinge wire harness a few years ago opting to route the harnesses inside the cargo area.

The lift gate wiper action is slow yet determined. I've lubricated the wiper shaft through the exterior bushing and not yet the interior lift gate wiper arm bushing. The ground connection though the liftgate latch and the hinges appears to be alright. The liftgate DEMIST grid works fine and fast.
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Yes, I remain in this vermin-filled structure with cracking exterior wall brickwork sheet hole as you see in the image somewhere in rotten Saint Louis, MO: