How to fix the bass sound muting issue in an upright piano (DIY).

[maxim_tuner]

• You can certainly fix this issue yourself.
  
  Here are the steps you need to follow:
  
  Check the 'Damper Adjusting Screw' on the 'Damper Block', as it may have loosened. Make sure the 'Damper Block' is in its standard position on the 'Damper Wire'. The 'Damper Block' should be aligned with the other 'Damper Blocks'. Using a long, thin screwdriver, carefully tighten the 'Damper Adjusting Screw'.
  
  If the 'Damper Block' has only slightly shifted (changed its angle to the strings), you can use your fingers to reposition it and then tighten the 'Damper Adjusting Screw'. In the video, the 'Damper Block' was only slightly shifted.
  
  Alternatively: Check if the 'Damper Head' has shifted. It is likely that the 'Damper Head' has become detached from the 'Damper Block'. Use any instant glue (even PVA) to secure the wooden 'Damper Head' to the wooden 'Damper Block'. Apply a drop of glue between the two components while pulling the 'Damper Wire' towards you. Then, using your fingers, press down on the 'Damper Block' so that it approaches the two bass strings. This will cause the glue to spread slightly to the sides. Ensure that the 'Damper Felt Wedge' has the same angle as the adjacent bass 'Damper Felt Wedge'. Let the glue dry for 10 minutes and avoid playing during this time.
  
  Test your repair. If the sound mutes immediately after the 'Damper Felt Wedge' comes into contact with the strings, you have successfully fixed the issue.

https://youtu.be/Z7KcadiMrs8