I don't suppose it could have been THAT bad as I've just watched it a second time to fill in an empty hour or two. I wish now that I'd made a body count of the Native Americans who got killed in attacking McBride's house, sometimes falling off their horses out of sync with the defenders' rifle shots: possibly twenty - a very high casualty rate. At least some of them were only wounded, in contrast to the apparent 100% mortality in similar situations in other films, and they were shown being helped away by their comrades.
I wondered about a right-handed Wade Harper firing his rifle and pistol from the right-hand side of the window, with his body protected only by a shutter. I would have thought that instinctively he would have preferred to have placed himself on the other side, behind the more solid wall.
The curious moving boulders have been mentioned by others. The Native Americans' English could have come from a child's comic book.
And who didn't think there would be an attractive young woman on the stagecoach ...