The upright piano hammer are clicking sound.

[maxim_tuner]

• The small felt RED cushion(the hammer butt felt ) was lose there. How fix it DIY.
  Yes, indeed, under 'the butt of the hammer' there is a small wood protrusion on which a small piece of fabric( the small felt RED cushion ) is glued there. The clicking is in sync with hammer bounce on return. This noise is from the hammer butt/jack impact. It’s either the hammer butt felt or buck skin. I am more than sure that the reason for it's click is there. I clear hear it's so.
  How fix it there:
  1 To free the hammer from 'the upright piano whippen'. (remove 'the hammer bridle' from 'the upright piano whippen' there).
  2 To unscrew 'the butt screw' and to remove the hammer from the upright piano action.
  3 If a piece of fabric is lost or peeled off there, then glue it back on.
  4 If it is good glued, but it is very hard, then try to revive it using a regular toothbrush.

[/https://youtube.com/shorts/lw_f6-WYkOc? ... ixS5DxK97i]