New 3DS XL ABXY buttons

I have had this system for a few years and had no issues with it before. But all of a sudden the “A” button started not working properly. It would work but only if I put enough pressure on it (when it doesn’t work it still makes the same clicking noise as a porperly working button). My friend and I opened it up and had a look inside but the buttons weren’t dirty and appeared to be okay. Any suggestions on where to go from hear?