My Minolta meter was giving erratic readings. I repaired it by dismantling the head and polishing the metal contact strips. All of them, because it as easier than figuring out just where the problem was.
I used a Dremel like handheld tool with a polishing disc and some metal polish. This removed the oxidation and the meter has worked reliably for a couple of years now, giving consistent repeatable readings. It wasn't necessary to unsolder any wires.