Arelith

I've had this happen a few times.

I currently have a belt with poison immunity and some poison based gas affects are automatic failures where I still lose con / or fail the affect. Not sure why.

I vaguely recall this being an ancient NWN bug.

Not sure if Arelith can fix it. I think it's usually stinky cloud affects like ghoul stench, poison gas auras on monsters.

Anyone else ever have this problem?

Correct me if I am wrong, but some Gas effects may apply a disease rather than a poison, same as some NPC's. I may be talking bullspit however.

Poisons got buffed awhile back so paladin immunity etc.. won't stop some poisons from effecting you.
It most annoying when you see mob spawn using this like spiders that "cast" poison and bypass the protection.
Shelobs lair is a prime example of where this happens.

Poison was buffed but they were never given any exceptions to immunity.

There are GAS based aura poisons on some monsters like Quagmire Ettercaps, some of the Yugoloths in Pandemonium, and a few undead which are not disease but versus poison. For whatever reason these auras poison immunity doesn't click off, but instead, you automatically fail and are given the penalty (usually con).

Any idea why this might be happening?