Not really sure what's the real problem of Maguire, but I think he always play under pressure and with that, he should be train himself very harder because he don't want to disappoint his teammates, coach and the fans. But as we can see, it's kind of not difference from one match to another.
Yeah Maguire received a bomb threat in few months ago, there's a fans so badly want to kick him from Manchester United.
No one knows for sure why Maguire has played so badly in the squad, even though when he was bought by Manchester United his performances were quite good and he was the first choice of the previous coach. Since the New Era under the tutelage of Erik Ten Hak in almost all the matches he played he made a fatal mistake which led to the defeat Manchester United. At the national team level, Gareth Southgate has given a stern warning to the player, if his playing time at club level does not improve then the opportunity to play in the main squad will be lost, even though currently the coach is still call him.
Maguire had experienced mental pressure at Manchester United because he made repeated mistakes and also received many threats from fans. I think the decision to leave was the best because maybe at a new club he will find his game again and not lose his place in the England squad. The question is which club is willing to offer him a contract, although new Chelsea coach Mauricio Pochettino once say he is interested in Maguire.