I had a button "weakness" on my Kindle 2, and Amazon replaced it, even though it was out of warranty. The micro-switches under those buttons can go quickly once they start to get mushy.
I have found that it is best to contact customer support via the website and get them to call you. You should be able to do that here:
https://www.amazon.com/gp/help/conta...node_id=508510
They usually call you back very quickly, and they'll have all of your info at hand.