Why does a key (A flat) make a clicking sound

[maxim_tuner]

https://youtu.be/ASOX6OtatP8
1 If you're getting clicks like that, it means the dryness caused the shank to shrink enough in diameter that it has loosened from the glue in 'the hammer butt'.
2 Or ‘the hammer head’ loosened glue off from ‘the hammer shank' too there.
How fix it DIY:
(2) 'A loose hammer head will make a slight clicking sound at the moment it hits the strings. Test for this by gently trying to move it up and down. A loose hammer head can be removed and re glued inexpensively. "The piano book" Larry Fine (page 138)' Introduction: Often when moving or transporting a piano, the hammer head (the striking part) of a hammer can become loose. This can result in misalignment, causing the hammer to either collide with neighboring hammers or become jammed, preventing it from striking the strings. You may also hear a distinctive sound when a loose hammer is in use, similar to a horse's hoof hitting cobblestone. Fortunately, fixing this issue does not require specialized knowledge or skills and can be done by anyone with careful attention to detail. In this guide, we will walk you through the steps to repair a loose hammer head. Max fixes loose hammer head of the upright piano there. See how he does it on the video 0:16 sec. there.https://youtu.be/HUD1rjRF4sA
Materials Needed:
1 PVA glue or similar wood glue
2 Small shim (e.g., toilet paper)
3 Basic tools for removing and reattaching hammer heads Procedure: Assessment: Start by identifying the loose hammer head. You will typically notice it by the erratic performance of the piano key associated with that hammer.
Disassembly: Carefully remove the loose hammer head from the hammer shank (the wooden part of the hammer 'shank').
Gluing: Apply a small amount of PVA glue to the inside of the hole where the hammer head attaches to the shank.
Shimming: Place a small shim (toilet paper works well) inside the hammer head hole after applying the glue. The shim adds extra tight to the connection.
Reassembly: With gentle pressure, slide the hammer head back onto the hammer shank, ensuring it aligns exactly as it did before. Pay attention to align it horizontally to make sure it strikes the strings evenly. You may need to adjust it left or right for proper alignment with neighboring hammers.
Drying: Allow the glued joint to dry for at least 2 hours, or as recommended by the glue manufacturer. Better 24 hours after the gluing up there. This step is crucial to ensure a secure bond. Testing: After the glue has fully dried, test the piano to ensure that the repaired hammer head strikes the strings evenly and produces the desired sound. By following these steps, you can effectively fix a loose hammer head on your piano. This repair should provide reliable performance for many years to come. It is advisable to use PVA or a similar wood glue for woodworking or fish glue tasks like this one.