Why is a grand piano key (E3) sticking? How to fix it DIY.

[maxim_tuner]

https://youtu.be/8U3rHcz9Nos?si=Hdk15FAeYLePgjI_
Max determined (he see it between strings there) that a sticking key in grand piano is caused by (E3) hammer (' the Hammer Head') partially resting on a neighboring hammer(' the Hammer Head') , preventing it from returning to its rest position on 'the Hammer Rest Felt'. Here's what to do to fix it:

1 Remove the grand piano action.
2 Loosen the screw of ' the Hammer Flange' that holds the hammer in place to align the flange of the hammer with the flange of the neighboring hammer use the screwdriver there.
3 Make sure that after aligning the hammer's flange, it (' the Hammer Head') doesn't rub against the neighboring hammer (' the Hammer Head') during its trajectory. The hammer should move freely from moment of its strike against the string and it's back to its rest position on 'the Hammer Rest Felt' .
4 Tighten 'the hammer Flange' screw in place and ensure its proper function there.
5 Carefully insert the piano action back into the piano.
6 Test if the hammer moves freely and the key no longer sticks.
Good luck!