I'm living with the trouble in my 84 for two weeks now. The plug housing can be opened up to put more "spring" on the contacts, but the heat generated by the flex board not making good contact causes the supporting plastic tongue it wraps on to melt, worsening the contact when the connector squeezes it.

The same principle causes the plastic behind the bulb holders to deform.

A new flex circuit board would be a waste in my case without somehow rebuilding the plastic it folds over. It hurts my lower spine to spend much time on it, so I think I'll pull the taillight assembly to work on it in good light and comfort.

I've had some success with cleaning the contact surface on the flexable circuit using a pencil eraser. In one case, I cut thin strips of thin copper foil and bent them over the worn contact area, then replaced the connector. This has worked for about a year now. You can get new flex circuits and just replace the old.