Sympathetic ringing

[Jerry Hunt]

On a 14 year old Yamaha G3, customer called complaining of some dampers
in the middle not damping. On investigation, discovered that the ringing
on was not from the note being played (there were about 4 in the center
of the piano), but was coming from un-muted trebles. Re-tuned 3 trebles,
eliminating most of the ringing. However, there was one not (F# 46) that
still produced noticeable ring in F# 70. Retuned this note, no change,
tried lowering pitch, sounded worse; raised pitch, sounded worse;
returned note to tune. This is the first un-damped note.

I would appreciate any tips on how this ringing might be eliminated or
at least reduced (damping duplex didn't make any difference).

Thanks in advance.

Regards,

Jerry Hunt