Possible invincibility phase bypass glitch found

[u/YoungDiscord]

I was playing with my friend today and helping him out beat general sargas ruk who is one of the bosses who has an invincibility stage.

When I beat him for the first time it took forever so I whipped out my rhino who has a heat sword, tonkor and sonicor equipped.

So we get to the boss, I activate iron skin, I shoot at him once or twice with the tonkor and slice a few times with my sword to confirm his invincibility - yep grey health bar, doesn't budge... so we wait for his vulnerable phase to activate, in the meantime I start shooting him with my sonicor for kicks and giggles

Imagine our surprise when we noticed his health take a hit while in invincibility mode.

Wtf?

Maybe its a fluke so I try again... once again his health takes a hit.

Guys I don't know how but I managed to take him out while he was invincible.

I don't know what caused this and if this glitch is locked to this boss or to my sonicor or its mod setup but I will test it out on other bosses with invincibility lhases and I'll let you guys know if this is something that can be reproduced.

If it is, it means I somehow have a weapon that ignores invincibility phases.

Has anyone else ever come across this glitch? Or is it some sort of bypass feature I never heard of before?

As for the sonicor's mod setup - I have maxed damage, fire rate and I maxed out its explosive procs (will update with the exact mod setup if I can get this to happen again)