When Westley fights Inigo, Fezzik, and Vizzini and when he runs off with Buttercup, he is wearing gloves.They are prominent when his fist passes Butturcup's face, which he describes as a warning. When he is pushed down the hill his mask and bandana come off as he rolls and when we see his hands again his gloves have disappeared and he is without them for the rest of the film.
When Fezzik and the others storm the castle, camera shots taken from their perspective, i.e, looking toward the mob and castle beyond, the castle's gates are securely shut. However, the shots of Fezzik from the defender's perspective are taken through the wide open gates.
After Buttercup pushes Westley down the hill, she throws herself down after him. Towards the bottom, her sash falls off and she's left laying on the ground. However, when Westley goes to speak to her, she is wearing the sash around her waist once more.
In the sword fight between Man in Black and Inigo, when MIB throws his sword down and then proceeds into his flip from the "horizontal bar" onto the ground level, he lands a good five feet from the thrown sword. In the next cut, he reaches a foot away to grab the sword's handle.
As Vizzini, et al, are waiting at the top of the cliff for the Man in Black to finish climbing, Vizzini wants to continue on and leave Inigo to battle the Man in Black. He becomes impatient and lifts his arms and tilts his head to his left and says "I'm waiting!". The scene cuts to a far away shot and we can see Vizzini with his arms still raised, but his head is not tilted to his right.
The belt/sash Buttercup wears changes right around the 14-minute mark. When she meets the trio in the forest, her belt appears to be gold and braided, worn empire-waist style under her breasts. It later becomes a brown beaded belt worn around her waist. It is unmistakable if you compare 7:40 vs. 38:41.
In the fire swamp, after rescuing Buttercup from the lightning sand, she and Wesley are hugging. In shots where you see her face, her left arm is over his right - but when you see his face, the arms are reversed.
When Vizzini cuts the rope at the top of the Cliffs of Insanity, he cuts if very close to the boulder it is tied around. Later when Inigo retrieves the rope to lower it down to Westley, the cut end of the rope is now several feet from the boulder.
On the castle wall, when Fezzik says "Doesn't that make you happy?", Westley turns his head to face Fezzik, but his head is still leaned away from him. In the next shot, however, Westley's head is leaned more towards Fezzik.
In the opening scene, the camera is behind Grandpa, looking over his shoulder, when he pulls out his glasses out, the book is open. When the camera is in front of him as he puts his glasses on, the book is closed.
When the grandson and grandfather argue over whether life is fair, in shots of the grandfather's face the pages of the book are flat. When the camera turns to the grandson, the top left page is sticking up and has the grandfather's thumb under it.
After rescue from the lightning sand and they are hugging, in a shot over Buttercups shoulder Wesley is caressing her face - but when it cuts to a wider angle from behind him, his arm is down at his side.
Multiple items shift positions in the grandsons room: the duffel bag and hardhat on the wall behind the bedroom door, a scarf and pair of roller skates on the shelf beside the TV, a T-shirt draped over the chair the grandfather sits on, and a baseball glove positioned on a bat in the corner between the bed and the window.
When Buttercup pushes Westley down the hill and she falls down after him, when they both come to a stop Buttercup ends up several feet farther down the hill then Westley. The movie then cuts to a scene of Humperdinck, then back to Buttercup and Westley. However, they are now shown to be right next to each other.
Clear landing pad in the first fight scene when they jump off the rock. The landing is elevated and one can see the rubber mat ripple as they land. The pad can also be seen when Inigo and Fezzik walk to the edge to look down at Westley climbing up.
Prince Humperdinck tells Buttercup his "entire armada will escort them on their honeymoon". She questions this, as he had promised to send his four fastest ships after Westley. Yellin, the captain of the guard, excuses himself from the room, bowing and saying "Your majesty". Humperdinck is still only a prince a this time, as it's before his father's death and would be referred to as "your highness". Majesty is only for Kings, Queens, Emperors and Empresses.
When the giant and Montoya go to the edge of the Cliffs of Insanity, to look down and see if Wesley is still climbing up, the last rocks they step on flatten, indicating they are made out of dense foam.
When Wesley & Buttercup come out of the fire swamp, Humperdinck rides up. Buttercup gets behind Wesley. When the camera is in front of them Buttercup is behind Wesley's right shoulder, when the camera is behind them she is behind his left shoulder.
When Westley and Vizzini have the Battle of Wits, Vizzini uses the correct term "Goblets" for the pewter vessels that contain the wine and Iocaine powder every time, except for the very last time before they drink, when he calls them "Glasses".
Vizzini mentions Australia's convict colonies during the movie. This may seem anachronistic since the movie has a medieval setting, but this story is fantasy not history. In fact, its being told as a fairy tale from a grandfather to his grandson. In the novel, this was just one of many (intentionally contradictory) clues about when the story takes place.
Prince Humperdinck correctly identifies the iocane powder after smelling it, even though the Man in Black had earlier described iocane as "odorless". However, the fact that it is odorless is likely why he "bets his life on it" to be iocane powder.
When Inigo hears Westley's cry of anguish (when the latter is subjected to the highest level in The Machine by Humperdinck), he explains that he knows the cry was made by the Man in Black, because the latter's true love is marrying someone else later that day. But Inigo has no way to know that Buttercup is the Man in Black's "true love".
When Inigo is explaining why is is looking for a six-fingered man, he says how the man had his father make the sword he is holding but then returned to get it and demanded it be sold for one-tenth the price. If he came to get the sword, why didn't he take it?
When Westley was trying to try climb up the Cliffs of Insanity there was a real easy way they could have made him fall. All they had to do was throw rocks down at him. Especially since Fezzik could throw huge rocks.
While climbing the cliffs of insanity, Buttercup's arms alternate from down at her sides (during the wide dummy shots) to wrapped around Fezzig's shoulder. It would be impossible for her to remove her arms from around his shoulder, as her hands are tied.
When Count Rugen tries the first thrust of his sword into Inigo (after Inigo pulls the dagger from his stomach); Inigo blocks the thrust and if paused, you can see Count Rugen's sword bend considerably when the cut looks at him over Inigo's shoulder (~1:25:55)
In the king's palace, Inigo battles four of Count Rugen's henchmen. He stabs all four of them, yet there is not a drop of blood on his sword. Later, while battling Count Rugen, his sword suddenly has a lot of blood on it, but this is before he has stabbed Rugen. Meanwhile, Rugen's sword has blood on it from stabbing Inigo, until it all disappears in one shot, and he's fighting with a clean sword.
When Humperdinck confronts Westley in Buttercup's bedroom, Westley stands up and points his sword at him. Notice, however, that when Westley raises his sword, the camera cuts away for a couple seconds to show Humperdinck's shocked expression, but then the cut back to Westley shows the sword positioned exactly where it left off before cutting away to Humperdinck - the couple-second interval was more than enough time for Westley to have raised his sword to full-height.
In the final scene, in the close up of the grandfather saying, "As you wish," the wall color is different from the color of the wall in the wide shot. This is because the close-up was a pickup shot done well after the original scene was shot.
Count Rugen is kicked after being stabbed by Inigo. He falls back against one of the dining hall tables, and his sword slides out of his hand. In the next shot however, just before he hits the ground, he is holding the sword again.
Inigo confronts Count Rugen and four attackers while Fezzik holds the man in black. Inigo kills the four attackers and chases Rugen. Whan Fezzik returns to find the man in black after breaking the door down for Inigo, the bodies of the four attackers are no longer in the same position that they were when Inigo killed them.
In the Pit of Despair, Humperdinck stands beside Westley as he lies on the table before The Machine. The dual-ended hose on the suction cups strapped to Westley's chest are facing forwards, away from his shoulder. But in the next shot, when Humperdinck talks to Westley, the hoses are facing backwards, with the hoses facing his shoulder.
When Westley is being tortured in the Pit of Despair, suction cups are attached to his chest. When Westley is rescued later, it seems the petechiae/bruises from these suction cups are only on his arms.
However, this is not bruising from the suction cups, this is the injury from the ROUS.
Count Rugen hits Westley on the left side of his head, towards the middle, to knock him out before sending him to the Pit of Despair. In the Pit, the bump on his head is on the right side of his forehead, but this might be from his fall.