I'd first confirm exactly what's triggering the overspeed condition before making an adjustment just to get it through inspection.
If it's only happening in the down direction under load, I'd be looking at whether the speed is actually outside spec or whether something in the governor/arrestor setup is causing it to trip prematurely. Condition and adjustment of the braking components would be worth checking as well.
I'd try to get the Artira service manual and verify the manufacturer's settings before changing anything. With a safety-related issue like overspeed, adjusting it by trial and error could create a bigger problem than the original fault.
