When West, Gordon, and the Ambassador transport out of the painting back to Morgan's place using the triangle, the triangle disappears with them. However, when they 'wake up' in front of the house, there is no triangle in sight.
Jim ties a piece of twine to the trigger of a revolver to fire it remotely. He pulls the twine a number of times to continually fire it. This would not work on a single action handgun. The hammer needs to be manually cocked to rotate the cylinder and reset the trigger each time before it is ready to shoot.
Near the beginning when they discover the jewels missing, when the 'dead' guard is touched he puts his hands forward as he hits the ground.
When the Gunman shot the bottle on Lightnin' McCoy table it should have killed him as well since it was also in front of him.
Artie meets Lightning McCoy in the saloon and says "yes I'm here to meet you", but there is no way that Artie could have known about Lightning McCoy because he had already left the house before Dr. Lovelace says anything about it to Jim. Mr. Morgan was the only one that he said anything to about it.