https://youtu.be/8Sp_2yIQILc?si=i8tzeUwJQE7CVtJd
- 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. 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.