NSX JR

The lighting for my ESP botton used to light up normally, meaning a soft red light behind each letter evenly. Now it lights up the top of the "S" and nothing else, like the light is a pinpoint instead of a mini-floodlight behind all letters. I know this is a nit-picking question, but what am I missing in my button to make it light up properly?

Yes, I have had the button cover off but can't find any missing parts laying around on the floor.