This seems to be caused by the expiry of the poison and the stun affliction occurring at the end of the turn, but before second wind sets in. To reproduce, apply crawler poison to an enemy. There should be 1 turn remaining on the poison, allowing the enemy to act before the poison sets in and stuns them. Apply Taser to enemy, preventing them from taking action that turn. Now, before the enemy's turn ends and before they gain second wind, they also gain Crawler poison stun, which lasts 2 turns. Presumably unintended.
