poisen immunity bugged, not working,

[Delaborga]

so i get hit by some poisen clouds and im immune to poisen with tiel and should be healing from it, instead it just ticks damage on me, 2 points gives me immunity, i still take a chunk of dmg from the poisen hit when its shot by an enemy, but rank 3 that should heal me from poisen damage just starts ticking on me instead and removes the immunity from rank 2