Both Charles and Edwards are able to run and jump aboard a moving train when neither could do so with the previous runaway caboose.
All the road signs are made of wood. Mr Edwards finds a piece of paper with instructions. But how did the paper survive during bad weather. Then Charles keeps that paper instead of putting it back, which will make it harder for other travelers to find out the instructions.
When Charles and Edwards deliver the Nitro explosives, it does not show if it was received by the railroad or other industrial business.
When Caroline is searching through the mail with Grace looking for a letter from Charles, she looks up at Grace and keeps flipping the letters. She could have easily missed the letter she was looking for by doing that.