David: I don not have the answer for you, however, I have been servicing a D with exactly the same problem of a false beat that did not respond to any of the usual fixes ( seating and levelling string, mating to hammer, etc.). I called Mike Mohr at Steinway and discussed the problem. In the end, the only remedy left untried was replacement of the offending string, which I have not done yet. I'm very curious as to whether you'll find a solution that I was unable to discover. Patrick Poulson, RPT
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