'DEAD' upright piano's keys F(4) and (E5). How fix it DIY.

I think that 'the wippen damper spoon' of the keys (E and F) was bad regulated there. May be 'the damper spoons' need lightly bend to from yourself to near it 'the damper lever' Read carefully how fix it ('The Damper spoon' misalignment.) see the instructions below there.
Additional issue: 'The Damper spoon' misalignment.
If 'the damper block' functions similarly to the video, where 'the damper spoon' has shifted, follow these steps:

1 Carefully detach the action unit from the upright piano for better access to 'the damper mechanism'.
2 Check the interaction between 'the whippen' and 'the damper spoon'.
Press down on 'the whippen' with your finger and observe if 'the damper spoon' catches 'the damper lever'.
3 Compare the differences between the neighboring damper spoons. To fix the issue, gently push on 'the damper spoon' and lightly bend it towards the front, closer to 'the damper lever'.
Conclusion:
By following the outlined steps, you can address the issue of the key producing a short sound on an upright piano. Remember to exercise caution when working with the upright piano and consider seeking professional assistance if needed.

HERE clip where tips of the same problem about and whole HOW fix it in 'TheMaximillyan' short video 'WHY one piano note sound short? It sound because it's 'damper head' has bad short move from strings'


Small problem with one note of the upright piano not ringing/resonating well. It has weak short sound because it's damper head has bad short move from strings there.
Introduction:
In a video, it was observed that when pressing the one of the key when is pressed, the sound is very short. Additionally, it was noticed that 'the head of the damper block' of it's the key rises less significantly than other keys there. This technical issue can be resolved by following the steps outlined below.

How to fix it yourself:

1 Ensure no foreign objects are obstructing 'the damper lever'.

2 Make sure there are no foreign objects underneath 'the damper lever', which could affect its movement.
3 Verify the correct positioning of 'the damper spring' for it's key.

4 Check that 'the damper spring' for the key is correctly placed on 'the damper lever', similar to the neighboring keys.
If 'the damper spring' has shifted, carefully use tweezers to return it to its standard position on 'the damper lever'.
Test the kinematic condition of 'the damper block' by pressing the key and observe its movement. Adequate lighting can aid in this inspection.
If the issue persists, consider removing the piano action from the upright piano.
If none of the previous steps resolve the problem, it may be necessary to remove the piano action for further examination and repair.
Alternative method: Adjusting the damper wire using a hollow tube.

If removing the action from the upright piano seems daunting, an alternative approach involves using a metal or plastic hollow tube (at least 10 cm long) with a slightly larger internal diameter than 'the damper wire'.
The tube should fit onto 'the damper wire' with a slight backlash, allowing for slight bending in the direction away from the strings.
Follow these steps to adjust 'the damper wire':
1 Remove 'the damper block' from 'the damper wire' by unscrewing 'the damper block screw' with a screwdriver.
2 Place the tube on 'the damper wire' and gently bend it towards you.
Once 'the damper wire' is bent, reattach 'the damper block' onto 'the damper wire', ensuring it aligns with the other 'the damper blocksThe hammers on those two notes are not letting off / escaping. They are blocking against the strings.

Possible causes:
1) Let-off is mis-adjusted. (Improbable, except if someone did so deliberately)
2) Felt punchings are missing from the let-off buttons.
3) Jacks are not seated properly underneath the hammer butts, e.g. because of broken bridle tape or missing butt felt.
4) Any other issue preventing timeous let-off (which should quickly become apparent to any technician upon inspection).

I would not classify any of these repairs as "DIY".
' and does not touch adjacent ones during movement.

regards, Max