Try with "3" and check if the issue persists, unfortunately glow stuff in L4D2 is very glitchy (specially the type 2).
If still bugs, I will need the map and position to "simulate".
Can't do much to fix the 2 type because the engine was badly coded.
What if we keep it as type 3 but prevent it from being visible through the walls? Can't this be done in some way?
I will provide information once I try and experiment. Thank you.