I have that in my BB too, different model bus than yours. Exactly the same instrument wise.
Get some electrical contact cleaner and spray the push on connectors and the whole board under the plastic barrier. soak it good and let it work the use a combination of wiping down, brushing, and compressed air to get at the hard to reach parts.
That board may not look it but is contaminated with all sorts of grime, oil smoke and dust bunnies.
Mine works fine except the tach never sits at zero when shut down. I can live with that as I have no fix for that.