The behaviour of Chao’s special is different for attacker and defenders. When Im attacking and I have a hero with a full bar at the end of my turn if I’m hit by the defending team’s Chao I lose mana and my ability to fire the special, as expected. However, when a defending hero has a full mana bar at the end of their turn and I hit them with my Chao they only lose their mana, they still get to fire their special as if the bar were full.
Edit: this only happens when the game ticks up the last bit of mana on the bar automatically, not when the bar is filled to full by tile hits. Also it’s not reacting this way on every hero and I didn’t note which heroes it happens with. I will add as that was info as and when I have it.