Corrected entry: As Aragorn and co. are riding up to Isengard (right after the title appears on screen), we see a long shot of Merry and Pippin sitting among the rubble. Not only are they on opposite sides from the subsequent close-up, they are also both wearing their jackets; in the close-ups, neither is wearing a jacket.
Corrected entry: When Gandalf and Pippin ride out of Edoras for Minas Tirith, the first shot is inside the stable as Shadowfax is galloping out the door. Gandalf's staff is in his right hand. In the very next outside shot from above the stable door, the staff is in Gandalf's left hand. He did not have any time to switch hands between these two consecutive shots.
Corrected entry: When Gandalf and Pippin arrive at Minas Tirith and go inside to speak to Denethor, he is holding Boromir's horn close to the mouthpiece. When Denethor stands up and starts yelling at Gandalf, however, the horn has disappeared from his grasp, with the exception of the horn's strap. (00:34:25 - 00:37:10)
Corrected entry: When the Mordor hosts has broken through the outer perimeters of Minas Tirith, a troll is hammering a large hammer at a gate. The sound of the hammer hitting the gate is delayed compared to the moment the hammer actually hits the gate.
Corrected entry: Just before the ride of the Rohirrim, we see a wide shot of them in their positions, not moving, and they are separated into two groups with a gap in the middle. In all further shots, the gap is not there.
Corrected entry: The journey from Osgiliath to Minas Tirith is about 15-20 miles. Faramir and his men were able to make the journey within a couple of minutes. This would be physically impossible for horses to do (even Shadowfax couldn't make the journey within a couple of minutes.)
Corrected entry: In the scene where Aragorn, Legolas and Gimli are standing in front of the entrance to Dimholt Mountain, their horses get frightened and run away with all their equipment save their weapons. Entering the tunnel, Aragorn suddenly has a torch in his hand. As it is not only a wooden stick, but a really big torch there's no way he could have hidden it in his clothes before. And it would not be logical if the dead living there kept torches for visitors at the entrance.
Corrected entry: When the heroes ride out of Minas Tirith to attack the Black Gate, there is a shot of them riding out of the gates of the city, with a fire burning the Witch King's fell beast to the far left of the screen. The problem: where has Grond, Mordor's giant battering ram, gone to?
Corrected entry: In the scene in front of the Black Gates, when Aragorn, Gandalf and the others approach the gates, their shadows show that the light comes from their left (which by the way is north). A few moments later, when Aragon is speaking to the soldiers, the light comes from the opposite side.
Corrected entry: Outside Shelob's Lair - before Orcs come and after Sam leaves Frodo: Apparently, Sam takes the Ring from Frodo when he takes him for dead. In order to do this, though, he would probably have to pull the chain over his head. This would be impossible because the web does not appear to be peeled back in shots after Sam has left Frodo. Even if he had simply yanked it from Frodo's neck as Frodo himself is seen doing throughout the trilogy, he would have to get it past the web on his chin. However, this, too, is impossible because that web is seen as still stuck fast to his chin and around his face afterwards.
Corrected entry: When Pippin is lying on a mat, just before he wakes up and steals the palantir, his body is the full length of the mat. On the mat next to him, which is the same length, is a full sized man, whose body is also the full length of the mat. As Pippin is a hobbit, he should be considerably shorter then the man in the next bed, but isn't.