D-Pad Left Button - Possible causes of light press not working?

Hello,

My left D Pad button of my ACNH Joy Con seems to intermittently not register a button press (both in game and using the button test function). I have realised that if I press down hard it will register the input, but a regular or light button press does not (but it works for up/down/right).

Nothing has ever been spilled on the joycons, the button doesnt stick and because of how I keep my stuff they practically look new. I tried dropping some isopropyl alcohol on the button and pressing it to see if that cleared anything but sadly not.

What should I be on the look out for? I have just ordered a kit so I can open the joy con and have a look so I'm hoping to be able to repair it.

Thanks all and happy holidays!