Problem with MacBook Air 13' 2018 built in Keyboard

Hi everyone,

I noticed that, when typing, there are some letters that have a problem: the "i" and the "u", sometimes, when I click them, two of them appears on the screen or they don't appear at all. I contacted the support and they made me do a combination with the keys, but nothing changed. I also cleaned the keyboard as showed on the Apple official website, but nothing.

Can anyone help me?