WHY the strings of the upright piano (C#2) resonating when hit the (C2)?

[themaximillyan]

It's (C) hammer is too far to the right there. When it's strick the string (C) It's hammer partly "touches" with string (C#) there too. Especailly it's we can hearing (C#) resonating sound more loudly when the sostenuto pedal pressed down there.
How fix it's:
1 Loosen 'the hammer flange screw' ( it's screw placed under hammer down there).
 2 Gently scoot 'the hammer flange' use screwdriver left and tighten it's.
3 Test it after as made (1,2). If resonating sound no you all made rightly there now.