The upright piano's hammers are getting stuck due to prolonged exposure to outdoor conditions.

The upright piano's hammers are getting stuck due to prolonged exposure to outdoor conditions. how to fix it DIY.
The prolonged exposure to humidity has likely caused the hammers to not return to 'the hammer rail' properly. The hammer's pin is tightly inserted into 'the hammer butt flange' bushes due to the previously high humidity. After striking the string, 'the hammer butt flange' presses on the rotating body part of the hammer, leading to the issue. This problem is exacerbated if the springs of 'the hammer butt flange' are torn or if 'the hammer butt springs' are missing.

If the hammer's movement is simply disrupted, you can fix it yourself:

1 Remove the action from the upright piano.
2 Unscrew the hammer.
3 Gently shake it by holding 'the hammer butt flange' and moving it up and down.
However, it's advisable to first remove the action from the upright piano. Then, use a regular hair dryer to gently heat along the front line of all the hammers. Set the hair dryer to the lowest heat setting. Alternatively, use a fan positioned to blow air directly onto the hammers. During this process, you can assess whether this operation is effective. Warm up several hammers and test by pressing from below 'the whippen' to force the hammer to move towards the string. If you notice a significant improvement, such as faster return to 'the hammer rail', the hammer is in good condition.

Additionally, you can simply open the lid and place a fan in front of the upright piano action for half an hour. This action may also be beneficial.

If these methods do not help, you can use "Max's method to fix old and tight upright piano hammers - How to loosen the shank from the flange" available at:    • Hammer 'butt flange' upright piano is...  "