Forcing open Finishers not working

[Damocles]

So I was researching arcanes and came across FINISHER procc arcanes. Since not every frame has built in abilities to open enemies to finishers and I do not prefer to bring a finisher sparring weapons/melee with finisher stances as I prefer to bring my Zaw. I read the wiki thoroughly for an old COUNTER ATTACK mechanic.

WHAT'S SUPPOSED TO HAPPEN
Basically if you are using MELEE + BLOCK + CHANNEL, and you run into close proximity of an enemy (armed with gun or knife but currently not working on corrupted) you will open them to a COUNTER ATTACK FINISHER only when they melee you (with knife or gun butt).

WHAT'S THE ISSUE
However, for reasons unknown, if you try this in simulacrum with invincibility on, it wont work. If you have invincibility off, it will work (sometimes because it's currently not 100% consistent). If you are not god mode but you have an ability like RHINO'S IRON SKIN on, that also makes it IMPOSSIBLE to COUNTER and OPEN enemies to FINISHERS.

NOTE:
This bug seems to be related to the animation of blocking bullets, as invulnerable frames do not swing their blocking melee animation while vulnerable frames will swing their melee in the blocking figure-eight pattern. This signifies whether or not the frame will open the finisher.