I've seen it several times the last days. I'm and adventurer and can only use calms (or is it mezzes? ) when mob is out of fight.
Typical scenario:
Red enforcer. Calm and run out of range so he cannot hit me and break the calm. Now when I get within range again, I get the "xxx attacks" message. I've tried to zone after calming to break any aggro, and mobs STILL attacks on sight (brown shimmering still around it).
So far I've seen this on enforcer and trader type mobs.