One key is not working - strange velocity behaviour

Sometimes can happen that one key of your instrument is not working or it has a strange velocity (too high or too low compared to other keys) or it can happen that it works in organ mode but it doesn't work in piano mode (for example for the Mojo61).

First... a little bit of explanation. The keyboards of our instruments are based on the "bubble contact" technology: there's a PCB under the entire keyboard, under every key there are 2 contacts. On top of them there's a "bubble (or rubber) contact" that, when pressed by the key itself, it will first close the first contact and then it will close the second one based on the leverage of the key. The time passed between the first contact closure and the second contact closure will determine the velocity (to make it simple, how high it will be the volume of the sound when you press that key... gentle press, low volume, hard press, high volume). Some sounds do not require velocity, for example the organ sound because you can't decide the volume of the sound based on how hard you are hitting that specific key: normally, in this case, when the first contact is closed (the upper one), the sound will start.

As you can understand, this is a mechanical part of the instrument: you have a plastic key with two actuators, a rubber contact and a PCB with the two contacts, all working together to ensure the correct playing experience. Mechanical parts can sometimes have faults: 

Normally, for keys not working or working in a strange behaviour you can face 3 scenarios:

1) What we call a "lazy rubber": just hitting that key with some force multiple times (you can also use your fist ) and see if it will "wake up". This can happen sometimes passing from cold weather to hot weather or contrary.

2) There's something (usually dust or little debris) between the contact board and the rubber or between the rubber and the key: in this case you have to perform a contact cleaning of the keyboard. Someone is able to do this DIY (there's a lot of youtube tutorials) or you need a tech. The same situation applies in case liquids entered the keyboard.

3) The rubber contact is faulty: in this case (very rare actually), you need a tech because the rubber contact or the PCB is faulty.

These videos are helpful to perform a DIY contact cleaning:

https://www.youtube.com/watch?v=rHOYktmxhZI&t=132s

https://www.youtube.com/watch?v=5m-q3jN4yeQ&t=18s