Viper Strike of the Mamba inconsistent/no damage poisons

Sometimes Mamba just seems to apply a 0 damage poison, this happens during normal mapping, single target, ubers, literally anywhere anytime and I have no idea what could be causing it.

Naturally if the target was poisoned it wouldnt get poisoned again but its very easy to see against uber eater here:

Clear example of me hitting, the boss losing energy shield (a sizable amount considering its poison with deadly ailments) but then taking no poison damage afterwards, while I get a reflected poison on me from the golden rule jewel: https://streamable.com/uawtj5

More examples of inconsistent/no damage and what the damage should look like when it does work: https://streamable.com/ze4me5

The build is unorthodox for where it gets its damage but having tried multiple configurations, different skills as well the problem seems to be exclusive to mamba and not other parts of the character.

Can confirm, am having similar issue. Recently made a mamba character, and this is happening regularly during low-level mapping, where I'm just whacking mobs to death with no prolif sporadically.
100% chance to hit, 100% chance to poison, basically unrolled maps so no block/immunity shenanigans. Haven't specced into Perfect Agony yet so crit shouldn't be a factor. Have Brutality linked to my movement skills.
I'm at a loss.

Can also confirm. This is my PoB: https://pobb.in/L9jpFNpM2AiO

I tried disabling perfect agony also, even tho i have 100% crit chance all times.

I tried playing with normal viper strike and i can see that poisoning is consistent. Please fix this, it feels super bad

Same problem here i dont know how to fix it i try everything i find to may do some issues in game but no results ... sometimes i do dmg sometimes i do not...

I seem to also be having this problem once I reach a damage breakpoint, when I give myself LESS damage I can poison again.

How many of you are using ward stack?

Also for me it doesnt seem to happen against full life monsters, but if they dont die from initial hit (like ubers) then I basically cant do poison to them. This does NOT happen when I have less damage though

Did some more testing, it seems to be right when the monster reaches low life. In fact, the current poison on it will stop doing damage at the point of low life. Its like the poison fizzles out.

Same here, sometimes zero mamba damage, sometimes normal on the same conditions