Why stuck the key of the upright piano? How fix it DIY.

[maxim_tuner]

On this video, we clearly see that one of the keys is sticking. What is the reason?
If you look closely here, you can see that there is a very small gap between this key and its neighboring key located to the right of it compared to the gaps between the other keys. Therefore, when we press this sticking key to make it go down, it rubs against the neighboring key, causing a simple jamming of the two keys.
What needs to be done to fix this by yourself:
The keys balance on a metal pin in the middle ('the balance rail key pin').
1 Remove this key from the upright piano.
2 Grab a screwdriver, set it against the pin, and give it a sharp tap to slightly push it towards the side.
3 If necessary, do the same to the key next to it.
OR:
1 Remove this key from the upright piano. (For convenience in work and subsequent operations, it is also necessary to remove the two neighboring keys on the right and left sides).
2 Shift 'the balance rail key pin' of the neighboring key, which is located to the right of the sticking key, slightly to the right using a screwdriver.
3 Place all three keys back into the keyboard to make sure that now all keys have a smooth movement and do not rub against each other or stick.
Be careful when applying pressure to 'the balance rail key pin' to avoid damaging it. If you are physically fit, you can perform this operation using only your fingers here.https://youtu.be/gsuJG-g5OHk

Good luck,