Why is one key pressed on an upright piano only, while a whole dozen sound there

[themaximillyan]

In this video where the pencil got stuck over the key bed of the piano, causing multiple keys to produce sound instead of just one. To resolve this issue, follow these steps:

1 Remove 'the upper front board' (you do find that there's going to be two little clips on eirther side you are going which need open there) and 'the fallboard' lift off too.
2 It may be necessary to remove 'the key's wood plank' which placed top all keys. (unfastening two screws on it’s sides using the screwdriver).
3 Remove the pencil.