I think I finally 'get' him. He plays on almost raw emotion and gets so engrossed in a game and its atmosphere/stakes that he's practically running on auto. I don't think there's even a moment's pause for: 'oh, I'm on a card, perhaps I shouldn't do that' in his head. You are always playing on a knife edge in that way, and until he can play and not become so emotionally invested, these "braindead" moments will keep on happening.
I don't know if you can teach someone how to not be like that; we generally say that the over invested/emotional eventually have something click in their own heads and before then, trying to make them think instead of just play takes a lot from their game.
We got away with it today, but he's cost the team a lot in terms of recovery and knock on effect, so it remains to be seen if we're going to fully come out of this unscathed. I hope a game like this will have had him look inside himself and ask 'what the feck is wrong with me!?' enough for him to want to do something about it, because the more this continues, the more certain it is he cannot be relied upon.