In Hemlock's house on the wall over his desk there are pictures of him on various climbs. One of these pictures is of him dangling from the rope by the railway tunnel door at the end of the movie.
The place in the desert where Hemlock leaves Miles is near the base of the needle rock that Hemlock and Bowman had just climbed, and it can be seen behind them when Hemlock stops his Bronco to let Miles out.
When urged to cut his line, Hemlock carefully removes his gloves, but they are back on later.
In the hotel at the foot of the Eiger, Jonathan looks out the window to see Pope surrounded by people at the outside tables yet in the long shot of the climbing team, the outside area is empty, yet when Jonathan goes outside to meet Pope, the area is again filled with people.
Hemlock loses his ice axe on the mountain, but it is visible strapped to his pack as he hands in front of the railroad tunnel window later.
On the practice/training climb on the rock column in Monument Valley, Hemlock is shown climbing 'up' and using existing anchor points, yet it is claimed that no one has climbed the formation before.
At the beginning of the training climb, the camera looks down on Hemlock as he starts up the face. The view below shows bright green vegetation and a parking lot with a large number of cars. After reaching the summit, the camera pulls back from the climbers and spins around in a panoramic view of the surrounding countryside revealing nothing but desert and brown scrub; the green vegetation and parking lot have disappeared.
(at around 44 mins) When Montaigne gets hit in the head and goes dead weight, his taught rope suddenly gets slack in Hemlock's grip.
At the end of the training climb in Arizona, when Eastwood hauls himself over the jagged top edge, then stands up, he is clearly on a different surface as the edges of the pinnacle are round.
When Hemlock meets Dragon, Dragon's right contact lens has moved to the bottom right of his eye in one shot.
When Hemlock shows Jemima the photo of Miles Mellough, Henri Bach and himself, two of the three have the flashes on their berets upside-down.
When the four mountaineers first encounter the ice and snow on the Eiger after the rapid weather change, they are forced to use their ice axes to be able to climb. During this scene there are various axe holes already in the ice whilst they are climbing upwards indicating that there had been a previous take of this scene.
Why Hemlock was not pulled by Bowman close to the rock wall before he cut the rope? So he would have fallen much less.
When driving on sand/dirt roads out in the desert, the tires screech as if driven on asphalt.
During the scene where Hemlock (Clint Eastwood) and Bowmen go on a training climb, Hemlock is 'leading' but there is a rope clearly visible above him and attached to his body.
At about 64 minutes into the film, Hemlock and Bowmen climb that high, thin, pillar-like formation, when Hemlock helps Bowmen onto its top, you can see the shadow of the camera, first on Bowmen as he crosses in front of it, and then on Hemlock's white t-shirt where for a moment you can also see the shadow of a cable as well.
When Hemlock is shown on top of the hill near the mountain resort where they will climb the Eiger, the down wash from the helicopter filming the shot as it approaches him can be seen blowing the grass around him as well as his clothes and hair.
As Hemlock enters the flat in Zurich (at the 22:47 mark) to carry out the first sanction, he takes a pistol out of a red plastic shopping bag and puts the bag on a shelf even though he is not wearing gloves. Investigators would not miss noticing it and could have gotten his complete set of fingerprints from the smooth plastic.
A minute later, after knocking the second man out the window, and he lands near witnesses, Hemlock leans out the window and gives the witnesses a long look at his face.
For someone with his experience, a professional assassin would never make even one of these mistakes that would make identifying him much easier, let alone two.