Vektrat, thank you for clarifying!


And also, I'd like to correct the condition I wrote above.

There's 2 conditions when skill "not working" bug appears.

1. Using "instant cast" self skill buff, such as Aetherflow. Bug rarely triggers when the buff skill is used then chained too fast by another skill.
2. Using "instant cast" debuff skill to enemy. Always happen when doing chain & spam skills continued by debuff.
Such as SMN skill combo Bio II > Miasma > Bio >> [Fester]
Give a little delay between Bio & Fester to avoid missing damage potential.
On this skill case, Bio DoT debuff takes few milliseconds before applied on enemy status, which is why I can't really tell it's bug or intended.

Slow-applied(delayed) buff also happens to Swiftcast, I believe this one due to the skill's animation.