I thought the no parry was due to the AI's resistance like in BG where some defenders resistance the stun after a successful parry (what makes it successful, green parry appears on ur side of the screen).
I did find it strange when I saw that I wasn't blocking, when I thought I was.
It is happening to me a lot against classic black panther , i believe is something related to his ability that cancels the stun when is an auto block but he is getting the same immunity against the normal parry . Other fights seems to be working fine.
OG black panther will fail AA when you have a bleed on you.
Each Bleed Debuff on the Opponent decreases their Defensive Ability Accuracy by 10.05%. Used to get me in AQ sometimes, 10% don't seem like much, but in this game it'll feel more like 50%.