Plot hole: The Bishop in the film is performing the duties you would expect of someone in his position (giving mass, hearing confessions, performing weddings etc.) He has his own private chambers in the cathedral, refers to Robin as 'the boy I knew' and talks about hearing his Father's confession four months earlier; so he's been around for a while. The problem is the credits refer to him as the 'Bishop of Hereford'. No explanation is ever given for why the Bishop of a city 100 miles away is living and working in Nottingham rather than looking after his own diocese; or why the Bishop of Nottingham isn't around to look after his. (The Bishop of Hereford was an enemy of Robin Hood in the original ballads, and it's likely the filmmakers just gave that name to the Bishop in the film due to its familiarity, without thinking about the plot hole this creates).
Plot hole: The assassin cuts a hole in the glass to kill the Federation president. But with the size of the hole and the placement of the scope on the phaser rifle, the assassin would not have been able to see out of the hole.
Plot hole: The helmet design is rubbish. The eyeholes are far too small - that close to the eyes the divider between the eyeholes would block almost a third of the wearer's vision. He would hardly be able to see what was right in front of him - and it is not too close nor too narrow to fall into the "blind spot" between the eyes. This is not a character error by Peevey - the helmet design came from the original plans - it is even shown in the German propaganda film!
Plot hole: When Frank gets the phone call that Bobby has been shot, all that is said is that Bobby has been shot on the street in Italian. They never said Richie shot him.
Plot hole: At the bar shootout where everyone except Marlboro and Harley are murdered, the two jump through the window, over the fence, into the airport, and into an airplane luggage compartment. They would have been caught by security. The missing, and dead, airport worker would have been missed and searched for, the gunfire would have attracted attention, and the police would have been called. They never would have left the airport.
Plot hole: How was Dolph able to start the car outside Yoshida's house after rescuing Tia? He didn't have a set of keys to that car, and he didn't hotwire it, so how did he get it started so fast, or at all for that matter?
Plot hole: When the police chief asks Joe 'where's the briefcase they were telling me about?' Joe tells him to look in the back seat of the white BMW. There are a couple of problems with this. First, the police chief is looking for a case with a bomb in it, because he received a phone call from the guy who had his BMW stolen. Even if he knew about the money, which is unlikely, the police chief has no way of knowing that the case he is about to open is not a bomb, since no-one saw Marcone steal the case with the bomb in it. Yet he opens it without calling the bomb squad. Second, Joe saw Jimmy put the case with the bomb in the back seat, so why doesn't he warn the police chief about it? (01:35:00)
Plot hole: No amusement park ride company would ever produce a prop scythe that was as sharp as depicted in the movie.
Plot hole: The famous line "There can be only one" is uttered in every Highlander film. At the end of the original, Connor obtained the prize by killing the Kurgan and being the last one. However, in this film and others, you find out that there are still others around, such as Duncan, the woman who was Duncan's girlfriend in Endgame, the other immortals following Jacob in Endgame, and the ones that showed up in The Source. So, why did Connor obtain the prize? He still wasn't the last one.
Plot hole: It's never really addressed or explained how Shredder survived his death in the previous movie from being crushed in a garbage truck.
Suggested correction: It didn't really need to be addressed, and thus is not a mistake. His hand emerging from the junkyard is enough to show that he survived his apparent demise at the end of the last film.
Plot hole: After Cali's father is killed the decision is made to cut power to the school so he or his men don't find out about his father. But if power was cut to the school then what is powering all the machinery in the kitchen that's providing food for 90 students?