The wild horses are captured by throwing a loop around their neck. Yet, when we see one of the horses on the ground, the rope is looped around the neck AND muzzle, to fashion a makeshift halter, revealing that the horse is halter broke.
When Guido is chasing the horses with the bi-plane. He pulls up a shotgun, and points and supposedly fires it. But, while there is a sound effect. The gun itself does nothing. No smoke, no movement, nothing.
When the rodeo PA announcer introduces Perce Howland [Montgomery Clift] on a bucking horse, he says Howland is from "White River, Wyoming." Howland corrects him with a shouted "California, not Wyoming." This reinforces Howland's remark at the pay phone that he was trying to call home but the operator kept giving him Wyoming rather than California. When Howland later mounts a Brahma bull, the PA announcer says, "Perce Howland of Black Hills, Colorado." Perce said he had recently been in Colorado, so the confusion of origins is understandable and perhaps intentional.
When the truck starts off to chase the mustangs, there are ten tires on the bed of the truck, five on each side. When Perce and Gay each rope their first horse and the tire attached to the respective lariat is slid off of either side of the truck bed, there are now only six tires, three on each side.
When the group gets ready to leave the house for the rodeo, as Clark Gable delivers the line, "honey, when you smile, it's like the sun coming up", directly under his chin an open doorway can be seen; just inside this doorway, a bushy haired crew member is clearly visible, and moves quickly to the left in an attempt to get out of the camera shot.
When Guido is herding the horses down canyon with his fixed-wing plane, there are aerial shots of the horses galloping down a two-track. The takes are shot directly behind the horses and the plane is flying at the same rate of speed as the horses. A fixed wing aircraft couldn't fly slow enough to match slower galloping horses.
In the supposed night scene where Gay is holding the flashlight while Guido works on the airplane engine, there are obviously multiple light sources illuminating the scene. You can see that the top of Gay's cowboy hat is lit from overhead as it casts its shadow down, yet the flashlight is lit from the left, as it casts a shadow onto Guido to the right. You can see the two production spot lights that are illuminating the scene reflected off of the glossy paint on the engine case.
As Roslyn and Gay are leaving the dry lake bed, they stop at the aircraft to retrieve Gay's dog. You see Roslyn jump into the truck and slide to the middle of the bench style seat, with the dog jumping in behind her. Although Roslyn's hands are down by her side, and the dog is between her and the door, the door slams shut. This is obviously due to a crew member closing the door right after the dog jumped in.
After Gay and Roslyn pick up the dog, you hear the truck engine rev and see the scenery behind them through the rear truck window start to move several seconds before Gay looks forward and makes any motion to start to "drive". The truck then lurches forward well after they had started forward.
When Gable, Monroe, and Cliff are standing in the back of the truck watching the horses with the binoculars, the clouds behind them change with almost every scene....from none, to one, to many. All taking place in screen time
of about 30 seconds.