Disklavier

Dear all, 

I wondered if someone could help with a niggling problem.

My Disklavier (DU1A) is emitting a vibrating sound from one of the circuit boards under the keys. I’ve notice there are screws with springs holding the boards in place. I’ve tried tightening a couple of screws - but I don’t want to damage anything. Any advice on this greatly appreciated!

Thanks
Kevin
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