I've had a bug pop up in a few battles. I have a Shadowblade with the leech trait in melee combat with undead. The undead hit the Shadowblade, and leech triggers. That's normal, I get the 8 HP back. Then another time she gets hit... and I see a row of blue 8's appear above her head, and her health-bar goes back to full. Combat log shows that she has been healed by the Leech trait more than twenty times.
The next turn, this happens again. And then again. Until I move her, she is instantly healing all damage she takes, the moment she is hit.