I've had a bug first happen to me while fighting the Black Crawlers. One of the enemies ran out of ammo but seemed to be trying to reload, unsuccessfully, getting the warning message "Out of Ammo!" about 8 times before giving up and passing his turn, doing nothing else of use. I presume that there is some timeout mechanic for enemy turns, or else he'd probably have tried to reload his pistol forever.
I also got a bug in the Ironhead base -
here is a save to test it out. Basically, attack Balor and observe as he does nothing - nothing at all during the entire battle, allowing one to kill him with ease. I suspect that he may be having the same problem as that Black Crawler, trying to do an action he cannot and eventually giving up. My suspicion is that the action is 'switching on his energy shield', perhaps, as Balor's AI worked just fine before I breached his shield. Thus I think that these two may be instances of the same bug.
Finally, an unrelated issue: the description of Last Stand states that you get two turns of full health. This is a little misleading IMO, since you only get one effective turn out of it: after you activate Last Stand, you get one turn where the enemies are trying to hit you at full health. After your next turn (i.e. at the
start of the enemies' next turn) your health goes to 1, meaning that if there are still enemies around, they're going to kill you if they hit even just once, and you don't really get a second turn. I'm not sure if this is an issue with how the skill works or the description, but one of them should be modified.