Corrected entry: It is revealed that Loki's scepter is holding an infinity stone. That would mean Thanos willingly gave Loki, a trickster he doesn't even know, the only infinity stone he had at the time. That makes no sense.
Correction: Thanos used Loki to gain the Tesseract, the space stone and gave Loki the mind stone to help the Chitauri invade Earth and retrieve the space stone for him.
Thanos has been searching for the stones for for a very long time, finds one, but gives it away to gain another. That makes 0 sense, considering he needs all 6 to complete his task.
As the other correction states, one stone alone isn't all that useful to him though. He can still exert control over Loki, so he's not giving it away, he's just providing Loki with a tool to get another one, then Thanos will claim them both.
Corrected entry: When the Avengers are defending the core, Ultron flies in and starts fighting Vision in real time, but pay attention to the left side of the screen: Iron Man is flying by in slow-motion. (01:56:25)
Correction: All the action on the ground is slow motion, Cap, Scarlet Witch's red power, the robots, not just Iron Man. So there's nothing to indicate it was real-time. It could have been done to show Ultron's speed, or just a style choice.
Corrected entry: Steven Rogers' dream scenes incorrectly display the order of his awards. CIB should be uppermost.
Correction: The timing of the event actually makes the award order correct. Referencing both Band of Brothers and veterans of the time you can tell the Airborne wings took higher precedence over the Combat Infantryman Badge.
Corrected entry: In the scene before the final battle, Bruce Banner is shown breaking into Von Strucker's castle/Ultron's base of operations alone. Immediately after, Banner is shown sitting in the jet with the others, then after being in the jet he is shown as being back in the castle yet again.
Correction: 1) Bruce does not break in alone, Thor helps him 2) The scenes in Sokovia take place after they arrive, and is intercut with clips of Captain America's pep-talk in the Quinjet.
Corrected entry: When Stark is talking to Steve Rogers in front of the new base, the door they came out of opens upwards, while a bit later you can see the door close sideways in the background when they stand next to Stark's car. (02:09:45)
Correction: The two doors are different. The door that slides closed sideways is the door to the garage after the car has come out of it, not the door the characters have just walked out of.
Corrected entry: When the Avengers attack the Hydra base in Sokovia, Stark orders in the Iron Legion to handle crowd control. The drones land in the city square and begin telling the crowd to remain calm in English, instead of the local native language.
Correction: The country in question is fictional and both Scarlet Witch and Quicksilver, who are from there, are fluent in English (the evacuees speak in English too), so who's to say what the official language is?
Corrected entry: During the end credits, the camera is constantly circling a marble statue of the Avengers beating Ultron. Early on, there is a close-up of Iron Man's right hand, and it's empty. Later on, in a much further shot, he is firing the repulsor from that same hand.
Correction: It's a stylized animated credits sequence and not a traditional scene. They're allowed to make changes if they want throughout the sequence for the sake of visuals without it being a mistake.
Correction: This isn't a plot hole, merely a plot point. Thanos needs all of the infinity stones. Realistically, the mind stone alone isn't much use to Thanos, but it gives Loki an advantage in acquiring the Space Stone. By using the mind stone, Loki is able to build a team of people to help him, and turn his enemies against each other and he was very nearly successful in achieving his goal. It is also made clear in the film that Thanos and The Other can punish Loki for failure without having to be on Earth with him. Loki's fear of Thanos would keep him in line.