[Ardratz]

The issue is simple, Vent Petale is only meant to work if you are dual wielding a sword weapon and a spear weapon and it does but it also works even if you are using two swords or two spears. It doesn't work if you just have one weapon equipped though. I checked my character screen with all of those combinations and the only time I wasn't getting the boost to skill and defense was when I had a single weapon equipped.

[Soapy]

Can't confirm or deny myself, but if it is bugged, keep dual type weapons in mind while fixing it.

[Neus]

This has been corrected.

Can't confirm or deny myself, but if it is bugged, keep dual type weapons in mind while fixing it.

Doesn't matter, Vent specifically says it has to be two weapons, so you can't just equip a Black Xyston and trigger it.

[Soapy]

I'm aware of that, but just making sure you still trigger it if you're using a Black Xyston and anything that counts as a Sword or Spear.

[Ranylyn]

Or Argus/Varon, considering; these weapons let Duelist Destiny use all it's toys (Sword/Spear for Duelist, Sword for Kensei, Sword/Axe for Ghost)