A single letter doesn't work properly on my laptop keyboard.

Hello,

Two days ago, the "S" letter of my keyboard stopped working properly.

When I simply press it, it doesn't work, but when I press it harder (punching it), it does, often writing two "s" at once, sometimes with a little latency.

I took away the mechanism behind the key, cleaned it, put it back, nothing changed. I noticed I even had to press hard on the "spring" behind the letter in order to write an "s", with the same results as before.

I haven't dismantled my keyboard yet (on a Pavillion DV6-2130ef).

What do you think? Might it be corroded? If so, is it fixable?

Thanks for any help.