DIY reduction of LED spillover possible?

[RadekPilich]

find my MRCC has horrible LED bleed / spillover, so much so that is difficult to distinguish whether there is a routing on a given output or whether it's a spillover from a nearby output.

I might consider taking the unit apart and putting some separators between the LEDs or wrapping them in electric tape or something along those lines. 

Has anyone done something similar? 
Is the internal design preventing similar solution somehow?