Why upright piano keys stuck. How fix it DIY.

[themaximillyan]

The pins ('The front rail key pin' and 'The balance rail key pin') that hold the upright piano keys in place may become loose or worn out over time, causing the keys to stick or not function properly, as shown in this video.
1 Debris, such as coins, buttons, or matches, may enter the mechanical parts of the upright piano action, leading to similar issues. It is necessary to locate and remove the debris.
2 In this video, it appears that the keys are sticking to 'the front rail key pins'. This can occur due to swelling, debris, key deformation, or a misalignment of 'the front rail key pin'. Sometimes, 'the front rail key pin' may not have been centered correctly during the piano's production, resulting in a slight offset. As a result, when a key is pressed,  'the front rail key pin' gets wedged against the cloth edge of the key's hole cloth bush.
3 Sticky materials like plasticine, chewing gum, wax, etc., can get on the keys. Additionally, small objects can become lodged in the gaps between the keys. In high humidity conditions, the keys may swell and rub against each other.
To fix the issue where 'the front rail key pin' of an upright piano is slightly offset and does not fully engage with the felt bush of the key (it hard moving there) when pressed, causing the key to become wedged and not return to its original position after release the key. You need remove the key and to use pliers with long and narrow jaws to reposition the pin ('the front rail key pin') to the standard position in one motion. There is no need to worry about doing this, as the pin is securely fixed in the wooden keypad and can freely rotate. Rotating the pin will resolve the issue of the stuck key.