Happy to help.
Sure sounds like some sort of a grounding problem. My guess would be the rear taillight grounds, as those are a common problem point. If you have the headlights on and hit the brakes or shift into reverse, do you ever get a slight glow at the indicator for the rear fog lights? That's a sure sign of a bad ground at the rear.
I would start by pulling the connectors at the tail light boards in the trunk. Inspect them for melting/browning and clean them well and it might temporarily fix the problem. If that solves the problem you can do what I did: I permanently fixed my tail light grounding problems by replacing the ground wires, which I documented in the thread below.
Holy melted taillight board, Batman!
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