My OH always falls asleep during an argument (if it’s in bed/bedtime of course). He works long hours and gets up at 5:30am so he’s understandably tired, BUT I just don’t understand how you can happily fall asleep mid-conversation especially if one or both of us is really upset.
He is generally a fantastic sleeper and can sleep on cue, which drives me mad as I’m an insomniac
But i can’t sleep (even worse than normal) if arguments aren’t resolved and I end up bottling everything up or sending huge rambling messages to try and get things off my chest.
I can imagine that drives him mad but AIBU thinking people normally can’t nod off 
Not little arguments like “who should do the dishes” but whalloping big “should we break up” ones