My logitech k800 has a key that is too sensitive

Hello, I bought a Logitech K800 about a month ago, but for the last two or three weeks, the "&" key has been malfunctioning. Just touching it and scrolling makes it display lots of &&&, or if I press hard on "a" or "é", it's the same issue. I tried cleaning the keys, but it seems like it's the plastic part underneath the key that is defective because even without the cap, just brushing against that plastic part makes &&&& appear. So I was thinking of calling Logitech tomorrow to claim the warranty, but I no longer have my receipt. So I have a few questions:

- Considering that the manufacturer's warranty is 3 years and that the keyboard was released less than three years ago, will Logitech replace my keyboard even if I don't have the receipt?
- If that is not possible, can I get this kind of problem repaired by a specialist, like a computer technician, etc.?

This keyboard has never been dropped, has never been exposed to any liquid, and I have never spilled crumbs or anything on it.

Thank you for your help because I'm currently experiencing GREAT depression.

Best regards