You're trailing with one goal and there's not much left of the game. So you change your team's mentality to Hard Attacking and make your formation extra offensive.
This works and you score a goal, tying the game, with only a few minutes left. Normally, a team would now stop being so ultra-offensive and tone it down but in this game a change takes about 10 in-match minutes to happen. Even if you change your formation and mentality to NORMAL, nothing will happen before the game ends.
This means that before the game ends, your team is so offensive that the other team manages to score again (sometimes even twice). I've lost games more than once like that. Really irritating.