Once Upon a Time in the West (1968)

Continuity mistake: During the last flashback that reveals Harmonica's issue with Frank and the significance of the harmonica, the harmonica in the boy's mouth is sometimes dented, sometimes not. (02:22:00)

NancyFelix

Frank: What do you want? Who are ya?
Harmonica: Dave Jenkins.
Frank: Dave Jenkins is dead a long time ago.
Harmonica: Calder Benson.
Frank: What's your name? Benson's dead, too.
Harmonica: You ought to know, Frank, better than anyone. You killed 'em.

Trivia: While Morton's private train plays a key role in the movie, and the train moves several times, the train's engineer and fireman are never shown, nor is any reference ever made to them.

Question: At first it seemed Cheyenne didn't know harmonica man, but later in the movie they help one another once to get the $5,000 from Cheyenne's bounty. Then Cheyenne rescues harmonica man from the train. And finally Cheyenne didn't want harmonica man to see him die they were leaving together I just think they knew each other and this was planned?