This seems to be a common issue specific to the green LEDs (all other colors are fine). There are mentions of replacing the LEDs with higher quality LEDs by soldering on new ones. I can confirm a few new LEDs work, but I haven't found a matching type of LED (intensity and "reflector" type).
The LEDs I have all appear much brighter, which is a concern. Additionally, they put out more light out the sides of the LED (less focused). Though, there appears to be ample light control in the rubber and buttons where it shouldn't be too much of a problem.
They appear to be 1.5mm 0805 SMD green LEDs with reflectors to minimize light leaking sideways.
Does anyone know the rough specifications (i.e. mcd @ 10ma, forward voltages, "reflector" type) or LED model number I can reference to match close to OEM? I will still replace all of the green LEDs.