Other mistake: Outside the Pine City marshal's office is a painted backdrop depicting some two-story blue-and-white buildings. The same backdrop is seen from the Virginia City saloon. It also appears in another town in the episode "The Legacy."
The Unwritten Commandment - S7-E28
Factual error: Wayne Newton sang "Scarlet Ribbons." "Scarlet Ribbons" wasn't written until 1949. The TV show Bonanza was set in the 1860s.
The Hostage - S6-E2
Other mistake: A gang kidnaps Ben Cartwright and holds him for ransom. He is chained to a post in an abandoned mine. When the men walk around inside the mine, the sound of their footsteps make it obvious that the floor of the mine is actually plywood covered with a layer of dirt. Additionally, when Ben finishes eating stew that was brought to him and sets the container down, it makes a loud "clunk."
Other mistake: Ben and Little Joe do not see the horse belonging to Ben's brother Will, who is staying with the Cartwrights. Joe says, "I'll see if he's in his bedroom." Joe is out of the scene for only five seconds, then returns and says, "He's not there." Five seconds is not nearly enough time to go upstairs, check a bedroom and come back downstairs.