Which keyboard assembly is faulty?

Question

Do it yourself

The keyboard, like the laptop, is over 6 years old. Used extensively but with care. Some buttons are rubbed to nice polished dimples. Recently, the keys began to fail at times, and many different ones at once. So I would like to know what could be the problem? If a certain key did not work, it is obvious that the matter is in its contacts, but why can several keys not work at once? In theory, after all, in the most mechanically loaded places there are key contacts, in other places there should be nothing to break.

Answer 1

film at the points of contact or cable. the type of keyboard or, at least, the laptop model could be voiced.
//so the keyboard is one node. there is nothing to share.

Answer 2

remove and blow at least from dust and food