At 37:00, McQueen goes to visit his old partner. He sits down at a table with him and takes out a pouch of tobacco and rolling paper. He opens the pouch and sprinkles tobacco onto the paper, then pulls the drawstring on the tobacco pouch with his teeth and throws the pouch on the table. Seconds later, in the next scene, the pouch is back in his hand and he repeats the same process.
A cigarette string in Wes McQueen's front pocket changes shape, position and then disappears altogether.
When Wes escapes from the jail cell at the beginning, and the lawmen rush into the cell and find the window bars sawed open with a hacksaw, they lift the window bars and they flex, obviously not made of iron or steel and clearly anyone could easily just tear them out by hand.
After the passenger cars with the lawmen are disconnected from the train, they start chasing the train on foot. After the safe is blown and Wes is getting ready to leave, the lawmen are almost to the baggage car. There is no way they could have covered the distance that the train traveled in such a short time.
During the attempted stagecoach robbery, some shots show tracks of wider pneumatic tires in the dirt, and not just wagon wheels.
In the scene after Wes McQueen and Colorado Carson leave the Winslow ranch, the U.S. Marshall tells the posse that McQueen may be especially desperate because he was wounded. The Marshall had no way of knowing this. McQueen had killed the man who had wounded him and the only people who knew that he had been wounded apart from himself were Colorado, who was in love with him, the loyal Mr. Winslow and his daughter. Mr. Winslow had spoken to the Marshall when the posse came to his ranch, and he said protected McQueen who was resting inside, saying he had ridden off while saying nothing about McQueen being wounded. The treacherous daughter wanted to alert the posse to collect the reward, but she was stopped by Colorado.