When Shecker arrives at the camp with his father in a flashback scene the other boys, including Goodenow,are all standing near each other.Which implies Goodenow is already with the guys in their cabin. But in another flashback scene Cotton brings Goodenow into their cabin saying he will be staying with them in the cabin and introduces them to the other guys including Shecker who is already there, but according to the earlier flashback scene should not be.
Near the end, after the buffalo are set free, the boys throw their arms around one another in a circle and spin. When the shot moves from wide to close up, the boys are in a different order in the circle.
When Teft shoots out the tire on the hustlers' Mustang, he threatens them by saying there are more BBs in the gun. But his rifle is clearly not a BB gun - it appears to be a .22 caliber rifle firing powder/bullet cartridges.