Pindelski ran a short repair story here once and I think he removed the temp guage and dropped some oil in on the center shaft. Said he used a jewelers tool to squirt the graphite in there.
I have that same proplem, cleaning the electrical connections fixed most of the problem, but it still jumps around sometimes.
Thinking to tear it apart sometime and maybe use a syringe with a good quality graghite lube and see what happens. Fixed my wifes anniversery clock using that.