It could be a case of really cheap batteries. Some brands of ultra-cheap double As have lifespans of an hour or less if you put them in a controller. GreyPilgrim's suggestion is good too as the battery housing can move around a bit during play. Bump it the
wrong way or shake the controller too hard and it will briefly break contact with the batteries, turning off the controller. Be a bit gentler with it during play and see if that helps things.
There is another potential cause and it could be game related. Previously when playing Assassin's Creed 2 my controller would cut out whenever Ezio jumped in water. No other situation would trigger this, but literally every time Ezio fancied a swim the controller
would turn off. It's unlikely in your case but it's worth a try. Make a note of how often it happens during play, and what specific situations trigger it. If it only happens occasionally when you get hit/take cover it's more likely a battery problem.
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