The frustration was there before they started leading and is like the players are truly not playing to instructions given by him because I see no reason why he would be uncomfortable each time Manchester United have a game, before 10-15 minutes you see him feeling like he's on a hot seat, what is really wrong with him? Even when his side scores you can never find him celebrate like every other coach does and that impression shows that he knows his team won't hold on to that lead for long and it will happen that the opposition side will equalize in no time, like this man knows he can't trust his players completely.
When Bruno was to take the kick Amorim was looking elsewhere, mehn...this man has lost the confidence of a true coach. I agree with you, with the machines they have winning with luck is something that's not suppose to be happening, and if you check is just few players that has that courage to keep on playing for the club without being frustrated on the field of play and Benjamin Šeško is one of the frustrated players, like he's not having the best of days at the club.