Disklavier

I wondered if someone could help with this?

 

I get quite a buzzing from under the keys on my Mk3 Disklavier. I have
stripped it down before and the cause is clearly the circuit boards below
the keys. However, I am reluctant to simply tighten them without knowing
what torque they should be tightened to. Or an idea of how tight I should
go. The screws are on springs if memory serves.

 

Thanks

Kevin