If my memory serves me, when I had a similar issue it turned out to be wear in the wires that run from the cabin into the driver's side of the trunk and end up at the license plate lights ... they pass through the hinge and over time wear in that area. I'd have to double check a wiring diagram and look through some of my old photos but I know I had to do that repair and I'm pretty sure that was the issue it was resolving.

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1987 300D, arctic white/palomino--314,000 miles
1978 240D 4-speed, Euro Delivery, light ivory/bamboo--370,000 miles
2005 Jeep Liberty CRD Limited, light khaki/slate--140,000 miles
2018 Chevy Cruze diesel, 6-speed manual, satin steel metallic/kalahari--19,000 miles
1982 Peugeot 505 diesel, 4-speed manual, blue/blue, 130,000 miles
1995 S320, black/parchment--34,000 miles (Dad's car)