When the con man is leaving town toward the end, the train schedule shows 'Ashville' listed on the chalkboard behind him. Asheville, North Carolina, presuming this is the city (since it's in the same state as Mayberry), is spelled with an 'e'. The name of the city is misspelled.
George tells Andy, that's the way the "Crookie" crumbles, then giggles, obviously the director chose to leave it in.
Since Andy is the sheriff, he could've run some sort of background check on Jones with outside authorities/agencies to find out if he was on the level or if he was some sort of conman.
In all the discussions about whether to trust George Jones or not, nobody bothers to ask why he's not investing any money himself.
By the 7th season, the viewer knows Sheriff Andy Taylor's character very well. The Andy that the viewer knows would never have invested with the crooked stranger who claims that he knows where the Civil War treasure is buried. Andy is always forthright and never tells a lie. However, at the end of the show when Goober asks Andy if he knows who the 5th investor is, Andy is vague and skirts the question.